Frank's N4SPP Hellschreiber page

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Tubes are thermionic "valves" in the Queen's English. "Tube" refers to the shape of the device, whereas "valve" refers to the function of a simple diode tube. Up to the mid-1930s, the German military used civil vacuum tubes for their mobile amplifiers, receivers and transmitters. Those tubes had actually been developed for civil broadcast radios and stationary telecommunication equipment. The tubes types that were deemed to nonetheless be usable, received additional markings to indicate their Wehrmachtsverwendbarkeit or Flugfunktauglichkeit (suitability for army or airborne radio applications). Cf. ref. 16. Still, they were not robust enough for general military mobile and field operation:

The Wehrmacht (and its predecessor, the Reichswehr) had a special agency, the Heereswaffenamt: the Army Ordnance Office. Its main responsibilities included the research and development, specification, testing, industrialization (procurement, logistics), and acceptance of weaponry, ammunition, and equipment, as well as the assessment of enemy weaponry. Ref. 20, 27. The office was dissolved at the end of April 1945. Heereswaffenamt is usually abbreviated to He.Wa.A, HWA, WaA, Wa. A, or Wa.A.

In 1933, the Heereswaffenamt instructed Telefunken (TFK) to start the development and production of a series of tubes, specifically for military applications. They had to be suitable for compact, powerful, mechanically and electrically robust telecommunications equipment. These miniature, special, and government tubes (Miniatur-, Sonder-, Spezial-, Behördenröhren) are collectively referred to as Wehrmachtröhren (sometimes spelled "Wehrmachtsröhren").

For readability purposes, RV 12 P 4000 will be denoted below as RV12P4000, without spaces. The first series production of this tube was a batch of 5000, in the fall of 1935 (ref. 21). Starting in 1937, other tube manufacturers were forced to also manufacture Wehrmachtröhren, including those developed by Telefunken (ref. 22). Valvo (Philips), and TeKaDe (TKD, Telefonapparate-, Kabel-, und Drahtwerke AG, in Nürnberg - Nuremberg in English, copying the French language in which there can be no "n" before a "b") produced the RV12P4000 and other types. The RV2P800 was produced by the same companies, and by Lorenz AG.

Ca. 1938, the Technisches Amt (Technical Office) of the Reichsluftfahrtministerium (RLM, the Air Ministry of the Reich, 1933-1945) began its own development and procurement of tubes, specifically for airborne applications (including missiles). This was primarily done due to the particular environmental conditions (e.g., temperature range, accelerations). This led to the "Wehrmachtröhren" being separated into "Heeresröhren" (army tubes) and "Luftwaffenröhren" (air force tubes). Each group had its own numbering / designator scheme (ref. 3, 4, cf. tables below). Note that this does not mean that army tubes could not be used by the air force, or vice versa. E.g., the universal RV12P2000 tube was widely used in army radios, but also in airborne communication & navigation radios and in the A4 ("V2") missile. Ref. 11, 16, 18, 21, 31, 39, 40. An estimated total of about 3 million of this universal pentode were manufactured from 1937 to 1956 (ref. 15). The Marine (Navy) had very few specific "Spezialröhren". During 1943 and 1944, the production volume of Wehrmachtröhren rose to an estimated 16.9 and 17.8 million tubes respectively (ref. 60).

Numbering scheme of the "Heer" Wehrmachtröhren
(click here - or on table above - to get full size)

Numbering scheme of the "Luftwaffe" Wehrmachtröhren
(click here - or on table above - to get full size)

Following the above numbering scheme, the RV12P4000 tube designator stands for:

Click on image above to get full 2-page datasheet

Pin-out of the RV 12 P 4000

The RV12P4000 is a pentode. The pentode was invented in 1926 by the Dutchman Bernard Tellegen (1900-1990), at the Philips Research Labs (Philips Natuurkundig Laboratorium, NatLab) in Eindhoven/The Netherlands. He also invented the gyrator (ref. 81); the Tellegen Theorem still is one of the most powerful theorems in network theory and the analysis of complex networks (electrical circuits, biological and metabolic networks, pipeline flow networks, chemical process networks, etc.) As the name suggests, the pentode has five electrodes - one more than the tetrode, which was invented by Walter Schottky (1886-1976, head of the Siemens-Halske semiconductor research labs around 1930). The tetrode has four electrodes: anode (a.k.a. "plate"), cathode, control grid, and a screen grid (a.k.a. shield grid). The applied grid voltage causes plate current to vary, whereas the screen grid effectively isolates the control grid from the plate. This reduces the so-called Miller Effect, that limits the tube's high-frequency gain. The pentode expands the tetrode with a suppressor grid between the plate and the screen grid. This suppressor grid eliminates secondary-emission current: stray electrons that bounce off the plate and cause an undesirable negative-resistance characteristic. Ref. 23.

It was common practice in Wehrmacht telecommunication equipment to use only one type of tube in all stages of most receivers (ref. 2). For instance, the circuitry of the Hell-Feldschreiber comprises four RV12P4000. The table below lists additional examples. This standardization had its advantages: lower cost (larger production volume) and improved logistics (few part numbers to stock, fewer spare tubes to stock per equipment, etc.) The down side of such standardization is the inherently sub-optimal use of the component in question. Using the same type of tube for AF-through-RF applications often implied the need for more complicated circuitry to work around the generic characteristics of the tube or operation in a sub-optimal region of its characteristics; sometimes a pentode is wasted by using it as a simple diode, etc.

Examples of radios with a uniform tube configuration
(the equipment may have other tube types, in addition to those listed)

During the war, tubes for civil radios (commercial and amateur) became scarce. Towards the end of the war, electronic equipment suppliers still had significant stocks of military tubes, and the Wehrmacht even hid radio equipment and spare parts at various locations around the country. After the war, surplus Wehrmacht tubes were used in home-built radio projects, and in "civil" broadcast receivers, (ref 29, 33, 34, 57) - often the original bakelite base was replaced with a "civil" base. These makeshift radios are referred to as "Notradios". Some examples of such commercial radios are:

As a side note, the Soviet Military Administration in Germany temporarily banned the use in (new) radios of Wehrmachtröhren, in a part of their occupation zone during 1946. Ref. 73.

1946 adverts that offer schematics and other services for using surplus Wehrmachtröhren
(source: Funkschau, Vol. 18, Nr. 1, June 1946, inside of front & rear cover page)

The actual glass tube ("Glasskörper", "Kolbe") of the RV12P4000, is protected and shielded by a perforated metal cylinder. This was initially made of extruded aluminium tubing. Later on during the war, this strategic material became scarce and thin tinplated steel sheet metal was used instead (0.3 mm "Weißblech"). The RV12P4000 (like the 4 mm narrower RV12P800 and the RL2P3, ref. 43) was nicknamed "Lockenwickler", i.e., "hair curling roller", as it resembled the personal-care paraphernalia of that era.

(length: 10.9 cm (≈4¼"), 2.95 cm Ø perforated sleeve, 3.25 cm Ø bakelite base, weight: ≈50 gr)

As you can see in the photo above, I have taken one of my RV12P4000 tubes apart. The disassembly starts with removal of the bakelite knob at the base of the tube. The knob is used for extracting the tube from its socket.

A color-coding scheme was used for about 16 commonly used Wehrmacht-tubes, the wrappers of their cardboard packaging, and a marking in or on the sockets. See ref. 7, 9, 13. This was done to avoid mistakes when replacing tubes in the field. This color is green for the RV12P4000, blue for the RV12P800, and white for the RV2P2000. For the RV12P4000, the color is applied to the manufacturers logo insert of the extractor knob. The insert of two of the four original tubes (those made by Telefunken) in my Hellschreiber are medium green; one of my Valvo spares has brighter green logo in its knob, as does my TeKaDe tube. My other Valvo tube has a green dot.

The top of two Telefunken RV 12 P 4000 tubes
(note the different TFK logos in the knob; the octagonal logo was used from 1926 until mid-1937; it was trademarked in March/April of 1937)

White triangle on the base of an RV 12 P 2000 RV 12 P 2000 with knob screwed into base

Removal of the RV12P400's extractor knob requires folding back four metal lugs that are inserted through the knob. The knob can then be pulled off the bakelite base. Note that RV12P4000 tubes made by Telefunken ca. 1935 had a white ceramic base and knob.

Removal of the knob exposes a small ceramic tuning capacitor ("Abgleichkondensator"), with a capacitance of several pF. It is connected between the anode and ground. The capacitor is formed by two crescent-shaped areas of metal deposit on a ceramic disk. After installation into the base of the tube, the capacitor was trimmed during manufacturing by scraping off part of the metal deposit until the desired value was obtained for that particular tube. This was done to make the tuning of the RF-circuit in which the tubes were used, independent of the individual tube (e.g., after replacement of the tube in the field)! The capacitor's disk has an outer diameter of 14.5 mm, inner diameter of 4 mm, and it is 1 mm thick.

The capacitor is easily removed, by de-soldering its leads from the pins of the tube. The next part to remove is a bakelite insulating disk ("Isolierplatte"). The disk is held firmly in place by the four lugs that also retained the knob. Part of these lugs is peened over onto the disk, to hold the latter firmly in place. This also provides additional stability of the bakelite base of the tube, and prevents the actual glass tube from moving down.

The inside of the retractor knob, and the bottom of the tube after removal of the capacitor

The bakelite disk has a so-called "Pressmarke". This small round marking identifies the factory and the material. See discussion further below.

A rubber cushion ("Gummi Puffer") is placed between the bakelite disk and the glass base of the tube. It is a piece of thick black rubber tubing (9 mm OD, 3 mm ID, 8 mm long).

Rubber cushion and glass base of the tube are exposed after removal of the "Isolierplatte"

The photo below shows how the four lugs are riveted to the bakelite base of the tube.

Once the lead-wires of the tube are de-soldered from the pins of the base, the bottom end of the tube is ready for removal of the glass tube. We now have to dismantle to the top end of the tube.

Top of the RV 12 P4000
(my 1940 Telefunken and the Valvo tubes have a white plastic disk on the top - all others brown/bakelite)

My two 1937 Telefunken tubes have grid pin (nr. 7) with pointed shape. All my other tubes (Telefunken and Valvo, 1940-1943, TeKaDe) have a rounded pin. I have measured pin length varying from 11.5 to 13.2 mm.

The first item to remove is a one-hole disk ("Lochscheibe") through which the grid pin protrudes. It has an OD of 28.5 mm and is 1.8 mm thick, with a 3 mm raised edge. The disk is usually made of bakelite, though there are also white plastic disks. The center hole is not a tight fit for the grid pin, so this disk is merely a cover plate. The disk is removed by folding back six lugs that are part of the perforated metal sleeve of the tube. With some effort, the disk can then be pulled out.

The rubber cushion, the bakelite top disk (bottom side shown), and the metal spring disk

The next item is a so-called shaft retention washer. This is a slightly cupped spring washer that is pressed all the way down onto the grid pin. This washer is not easily removed, as it is designed for tight-fitting, one-way installation.

The top of the tube after removal of the 1-hole disk (left) and the shaft retention washer (right)

The retention washer sits on top of a 4-hole bakelite disk. Note that the grid pin is not press-fit into this (brittle) disk, but the disk is molded around it (see cross-section photo towards the top of this page). The disk is relatively thin. It does not provide much hold for the grid pin when force is applied to it, e.g., when inserting the tube into, and pulling out of its socket. So, the function of the retention washer probably is to immobilize the grid pin, and distribute contact forces over the disk. The grid lead-wire that comes out of the top of the glass tube, is soldered into the grid pin. This disk is also tightly fit into the perforated metal sleeve of the tube. The grid lead-wire is either de-soldered or broken off while removing the disk.

The 4-hole bakelite disk with grid pin (left) and the top of the tube after removal of that disk

At this point, we can see the very tip of the glass tube peaking through the hole in the black rubber (or substitute rubber?) stopper ("Gummi Hülse"). The concave side of this vibration damper rests on top of the glass tube.

This rubber piece is 18 mm high, and is simply pulled out. The upper third part of the glass tube is shielded with a sheet-metal sleeve ("Metall Hülse"). It is 18 mm high and 0.2 mm thick. Both this sleeve, and the perforated outer sleeve of the tube, are connected to the same contact at the base - with a thin multi-strand copper wire.

The glass tube is now pushed out the top of the outer sleeve. There are no markings whatsoever on this glass tube.

The bottom of the glass tube was resting on another vibration damper: a blue rubber band ("Gummi Ring"). it measures 5 mm in height and is 1.7 mm thick, with scalloping on the inside.

The perforated metal sleeve is fixed to the bakelite base of the tube in six places: holes into the sleeve are pressed into slightly larger holes in the bakelite base. After drilling out these holes with a 3.2 mm bit, the sleeve can be pulled off the base. As clearly visible in the photo immediately below, the tinplated sheet-metal sleeve of this TeKaDe tube, has a longitudinal seam that is soldered. All my other RV12P4000 tubes have a perforated sleeve made of seamless aluminium tubing.

The perforated sheet metal sleeve of an RV 12 P 4000 made by TeKaDe - note the soldered seam

Tubes like the RV12P series (4000, 2000, 800) represent a transition in tube construction and manufacturing technology. They have a button-stem rather than a pinch-stem. The pinch-stem is also known as "pinched stem", "crimped stem", and "press stem" (D: "Quetschfuß", NL: "kneep"). The stem is the bottom part of the glass tube, where the lead-in wires are passed through to the electrodes. The conventional pinch stem was - and still is - the standard for regular incandescent light bulbs, gas discharge lamps, and halogen lamps. As tubes were originally developed from such light bulbs, it is logical that the same manufacturing technology was used.

(source: part of Brimar Valves company advertising in Wireless World, March 1943)

A pinch-stem is made by a sequence of basic manufacturing steps (ref. 32, 38, 74, section 42.2 in ref. 75):

Annealing (heat treatment) steps throughout the manufacturing process ensure that strains and stressed in the glass are removed. To retain the vacuum seal, the lead-in wires (or at least the part that is fused into the glass) must adhere to the glass and have the same thermal expansion coefficient and expansion rate as the glass. Copper-clad wire made of a nickel-iron alloy has the required properties. Cf. section 42.2. in ref 75. This is called "dumet" wire, for "dual metal". It was developed ca. 1911, and can be used for wires up to 0.5 mm in diameter (≈ 1/64"). Related alloys are "cunife", made of copper (Cu), nickel (Ni), and iron (Fe), and "fernico", made of iron, nickel, and cobalt (Co). For lead wires through quartz glass (gas discharge lamps, neon lamps), molybdenum wire or strips are used instead.

Clearly, with the pinch-stem construction, the wiring between the contacts and the electrodes of the tube is relatively long. In the stem, the lead-in wires are parallel and closely spaced - especially so, in a tube with a larger number of electrodes (pentode, heptode, etc.). Each wire has self-inductance that depends on the wire's length. Between the wires (and, hence, between the electrodes) there is undesirable capacitance. The self-inductance and capacitance limit the operating frequency of such tubes to VHF. Ref. 22, 25, 35. The parasitic capacitance in the stem also depends on the dielectric constant of the glass, which varies with the operating temperature. The lead-in wires are arranged in a straight line at the top of the pinch. This makes the attached system of electrodes mechanically less stable, and more susceptible to vibration and shock, especially in a direction perpendicular to the long side of the pinch.

These limitations were mitigated with the introduction of the button stem (D: "Preßteller"), which was also used in the "Stahlröhren" (ref. 21). A button stem starts out as a pressed glass disk, with small holes that are evenly distributed around the edge of the disk, like a button for clothes. Hence the name. The lead-in wires are passed through the holes and fused to the glass. Button stems are typically at least 1 cm (≈ 3/8") shorter than pinch stems. There are two basic forms of "Preßteller": the "Scheibenfuß", and the "Napfpreßteller" or "Napffuß". The prior is a button that is simply a glass disk, whereas the latter is a button with a raised edge. Ref. 35.

Button stem glass tube bases: "Preßnapf" (L) and "Preßteller" (C and R)

Initially, the lead-in wires were still connected to contact pins of a tube base. Later on, the tube base (D: "Sockel") was dispensed with altogether to create the all-glass tube (D: "Allglasröhre"), where heavy-gauge lead-in wires or dumet pins serve as connector pins. Ref. 79, 80.

The RV tubes are among the very first series-produced tubes in Europe with a button stem. However, button-stem and all-glass technology had already been used in (almost) all-metal tubes ("Stahlröhre"), "peanut" tubes, and "acorn" tubes (D: "Eichelröhre") such as the "955" miniature triode developed by RCA in 1934 (ref. 66, 67). The latter was suitable up to low-UHF (≈ 600 MHz), and was also used in 1935 by GEMA-Berlin ("Gesellschaft für elektroakustische und mechanische Apparate mbH") in their early radars and radio telephones (ref. 78). The origins of practical miniature tubes go back to the South-African Hendrik van der Bijl in 1919, who further developed his technology in 1923 at Western Electric, to create the 215A "peanut" triode. Ref. 76, 77.

The RV12P4000 tubes are inserted "head first" into a so-called "Patronenfassung". Literally a "cartridge socket", probably named so because the sleeve (turret) part made it resemble large caliber ammunition. The sleeve keeps the tube properly aligned during insertion and extraction. The sockets are installed in such a way, that that the tubes can be removed without opening the equipment housing - very convenient for maintenance!

The molded tube sockets of the Feld-Hell's electronics box are made entirely of bakelite. The socket is installed into the equipment chassis with two screws through the flange at the entrance of the socket. The old plumbers adage about tightening pipes and screws is appropriate here: "Nach fest kommt ab" (after "tight" (it) comes "off"). Over-tightening of the mounting screws cracked the mounting flange of the socket. This construction with relatively brittle bakelite was not robust enough for military operation. Later equipment had a socket with a sleeve made of perforated sheet metal, and an adjustable mounting bracket.

Top of the Feld-Hell tube socket, without and with an RV 12 P 4000 inserted

Note that a notch ("Nase") protrudes from the side of the base of the tube. The tube can only be inserted fully into the socket and engage the contacts, if the notch is aligned with the corresponding recess in the socket. A simple and effective fool-proofing method.

A perforated aluminium socket - one of the retainer springs is visible inside

According to the Telefunken datasheet for this tube (ref. 10), the socket has part number ("Lieferung-Nummer, Lg.-Nr.") 1670. Some sources refer to this as T1670, where "T" probably stands for Telefunken. They also call out other sockets with part numbers D3487, D3615, and WG6. There is also an adjustable mounting flange, with Telefunken part number 1795. The bakelite socket does not require a separate mounting flange, as it has an integrated bakelite flange. The aluminium socket shown above, does require a mounting flange or bracket. I have not found any part number markings on the bakelite and aluminium sockets that I have looked at, nor any authoritative literature that specifies the above part numbers. The RL2P3 (a low-power ("QRP") transmitter tube), uses exactly the same socket (ref. 42).

The RV12P4000 - and similar tubes - has conically shaped brass contacts ("Kegelkontakte") that protrude radially from the bakelite base of the tube. The next generation of Wehrmacht tubes, such as the RV12P2000, dispensed with the perforated metal sleeve, and had cylindrical radial pins ("Seitenstiftkontakte"). See photo above.

Special thanks go to Werner Thote, DL1VHF, who has provided me with invaluable information regarding the tube markings.

Example of manufacturing, acceptance, and property stamps on a Valvo RV12P4000 tube

The Reichswehr and the Wehrmacht had a special agency, the Heereswaffenamt: the Army Ordnance Office (cf. ref. 51, 82, 83). Its main responsibilities included the research & development, specification, testing, industrialization (procurement, logistics), and acceptance of weaponry, ammunition, and equipment, as well as the assessment of enemy weaponry. Ref. 1, 2. The office was dissolved at the end of April 1945. Heereswaffenamt is usually abbreviated to He.Wa.A, HWA, WaA, Wa. A, or Wa.A.

All weaponry, ammunition, and equipment delivered to Wehrmacht was subject to pre-delivery testing, inspection and acceptance. This was the responsibility of the Heeresabnahmewesen, the Army Acceptance Organization. Inspections were performed according to detailed guidelines called "Technische Lieferbedingungen", the technical delivery specifications. These were prepared by the respective "Waffenprüfämter"(WaPrüf), the weapons test departments. The Abnahmewesen comprised a large number of Heeresabnahmestellen (army acceptance / inspection stations, ordnance detachments). The Abnahmestellen were typically regional inspection stations, covering multiple equipment suppliers and factories. They were often co-located with the factory of a major manufacturer, but not staffed by employees of that manufacturer. Each Abnahmestelle had a unique identification number of up to three digits. Note: this identification number does not represent an individual inspector! Each accepted item was marked with an Abnahmestempel, a stamp to indicate both Prüfung (test/inspection) and Übernahme (transfer) by the Wehrmacht. The stamp consists of an eagle-above-swastika symbol, "Wa A" and the identification number.

The RV12P4000 tubes in my collection, and those that I have seen "in the wild", carry various WaA aceptance stamps:

I also have Telefunken RV12P4000 tubes from 1940 without a Waffenamt stamp. This is rather unusual.

An other possible acceptance stamp on Wehrmacht tubes and equipment is "BAL". According to Luftwaffe service regulations (ref. 58), this stands for "Bauaufsichts-Leitung" of the German Air Ministry ("Reichssluftfahrtsministerium", R.L.M., 1933-1945), or "Bauaufsicht-Luft(waffe)". Some literature claims that B.A.L. stands for "Beschaffungs-Amt für die Luftwaffe", for air force procurement agency. The BAL stamp comprises the abbreviation "BAL" and the number of the acceptance authority, both placed inside an octagon. Though fully independent organizations, the BAL and WaA did coordinate their tube acceptance activities. Tubes from Valvo, Lorenz, TeKaDe (TKD) and Telefunken/Erfurt only carry a WaA stamp, whereas tubes from Telefunken/Berlin only carry a BAL stamp, e.g., BAL 716 or 1964. Tubes from Philips/Eindhoven typically also only carry a BAL stamp (BAL 1790), though sometimes they were retested at Valvo/Hamburg, where they received a second acceptance stamp (WaA 745). The "Kriegsmarine" (navy) did not have its own acceptance stamps for tubes, but tubes and equipment may, of course, be marked with the "Kriegsmarine" property stamp.

Acceptance stamps used on other Telefunken tubes are WaA 716, BAL 716, BAL 964, BA 6933. Valvo WaA 584, WaA 801, WaA 4801, BAL 1790. Opta: BAL 913, BAL 2879, BAL 11328. Lorenz: BA 4721. Cf. pp. 42-44 in Ref. 18.

As the old saying goes: "The great thing about standards is that there are so many of them." This also applies to the formats used for the date stamps. Most common is a single date-of-manufacturing stamp (D: "Herstellungsdatum"), with a "ww/yy" format. For example "11/40" means week 11 in 1940. However, the same date stamp could also be formatted as "11. 40", "11.40", "11 40", "1140", or "11-40".

Some tubes have two date code stamps, e.g., 42/43 and 45/43. The second stamp is the acceptance date (D: "Abnahmedatum") - sometimes as much as a year after the manufacturing date. The two dates need not have the same format, e.g.:

Some tubes made by Lorenz have the date (and other markings) engraved or etched into the glass tube, or engraved into the bakelite base, rather than stamped. Sometimes the date includes the day as well.

Note that there are documented cases of Wehrmacht tubes where the acceptance stamp actually pre-dates the manufacturing stamp! This may have been done as part of a scheme to show compliance with production targets.

The major tube manufacturers all had multiple manufacturing locations. The date-of-manufacturing stamp is often expanded with an indication of the Röhrenwerk (RöW, tube factory) location. On Valvo/Philips tubes, this is typically "H" for Hamburg, "W" for Wien (Vienna/Austria), "WW" for Weißwasser, and "E" for Eindhoven/The Netherlands. The letter code is placed after the date code, except for "W", which is typically placed in front of the date code.

Telefunken had quite a number of Röhrenwerke, e.g., Berlin (multiple Werkstätte), Erfurt ("E" or /4), Ulm ("U"), Neuhaus am Rennweg ("N" or /2), Lodz/Poland ("L"), Prague/Czechoslovakia - now Czech Republic ("Pr"), Mülhausen, and Rudolstadt. Tubes manufactured at the Neuhaus plant were often accepted at nearby Erfurt.

The Wehrmacht tubes normally carry an "Eigentum" ("ownership" / "property of") stamp, to indicate that it was produced for - and owned by - the Wehrmacht in general, or by a specific branch of the Wehrmacht: Heer, Kriegsmarine, or Reichsluftfahrtministerium (as a proxy for the Luftwaffe). Typically, the stamp is one of the following:

The stamps are typically black. However, the "Eigentum RLM" stamp on two of my Telefunken RV12P4000 tubes is magenta, which is very unusual. These tubes also have no Waffenamt stamp...

Two of my RV12P4000 tubes, have the number "2" and "4" stamped directly below the WaA 745 stamp. They were manufactured at Valvo in Hamburg in 1941. I have also seen a 1940 RV12P4000 from Valvo, with a separate "7" stamp below the WaA 745. The number "3" has been used on other Wehrmachtröhren from Valvo. It is not clear what these numbers refer to. Valvo did have multiple manufacturing locations in the Hamburg area (Lokstedt, Stellingen), and a particular site may have had multiple manufacturing lines for the same tube.

Some tubes have a 4- to 6-digit code stamp in addition to the date-of-manufacturing stamp. Most likely, the first digit refers to a Telefunken manufacturing plant. E.g., "1" implies Berlin, "2" Neuhaus, "4" Erfurt, "5" is for the AEG/Telefunken Röhrenfabrik Berlin-Oberschöneweide/Oberspree (RFO), whereas "8" implies "manufactured for Telefunken by Philips/Valvo". The rest of the digits are probably a running serial number. The 4-digit codes may have been used for tubes with a modification that had not yet been homologated.

(three Telefunken RV12P4000 tubes; far left with date code 31/37, the other two 24/40)

Most of the bakelite press-molded parts of the tube, as well as the bakelite tube socket, carry small round embossed molding marks. They are so-called "Preßmarken", "Prägezeichen", or "Prägemarken".

The entwined S-H on the left is the standard Siemens-Halske logo marking of that era. The second one is a "Kunststoffkennzeichen", an industry standard marking for molded items. It comprises a two-digit code (either two figures, or one letter + one figure) to identify the "Presswerk" - the factory where the material was molded, and a letter or number to identify the actual material. Ref. 19. Here, the factory code "34" denotes Siemens-Schuckertwerke, Abteilung Isolierstoffe, in Berlin-Siemenststadt.

The "S" denotes "Phenolharz mit Holzmehl als Füllstoff". This is a moldable phenolic resin (PF), reinforced with sawdust filler. This is usually referred to as "bakelite". Ref. 46, 47. Bakelite was patented in the USA in 1907 by the Belgian Leo Baekeland (1863-1944), who emigrated to the USA at the age of 26; his patent expired in 1927. Hans Lebach filed patents in Germany for a virtually identical material ("resit"), several months before Baekeland did so in the USA. Extensive patent litigation ensued (ref. 22). PF-related patents actually date back to the late 1890s, though it was Adolf Baeyer (later changed to von Baeyer; not to be confused with Friedrich Bayer, founder of chemical giant Bayer) who had already discovered in 1872 that formaldehyde and phenols can be processed into a hard resin. Baeyer did not commercialize his discovery. Note that bakelite is not a cheap or inferior material! The customized molds are very expensive, as are the molding presses. However, bakelite was competitive, as durable items with complex shapes could be mass produced, without post-molding machining such as drilling, grinding, sanding, turning, or polishing (though a shiny surface was required not for military products). Also, the wood dust filler is not a cheap ingredient at all, given the required fineness of the powder. Towards the end of the war, good wood dust became scarce, and the quality of the bakelite products declined.

The material identifier "T" was used for phenolic resin reinforced textile, often cotton. It is referred to as "Hartgewebe" (hard cloth), with brand names such as Turbax and Harex. In Feld-Hellschreiber machines, this material is, e.g., used for gear wheels.

The molding mark codes are placed within the stylized initials "MP" or "MPD", which stands for MPAD, the "Staatliche Materialprüfungsamt zu Berlin-Dahlem" - the State Materials Testing Institute at Berlin-Dahlem. The institute was founded in 1904, as a merger of three royal testing institutes: the "Königliche Mechanisch-Technische Versuchsanstalt" (M.T.V.), the "Königliche Prüfungsstation für Baumaterialien", and the "Königliche Chemisch-Technischen Versuchsanstalt". Most of the building shown below still exists today, and is home of the "Bundesanstalt für Materialforschung und -prüfung" (BAM), the Federal Institute for Materials Research and Testing.

Materialprüfungsamt, Berlin-Dahlem, 1904 - as seem from Potsdammer Chaussee
(source: p. 5 in ref. 45)

The industry standard dates back to 1924, when it was established by the members of the "Technische Vereinigung der Hersteller typisierter Preßmassen und Preßstoffe" (T.V.) - the "Technical Association of Manufacturers of Standardized Molded and Compression Molded Materials". In 1938, this association was later changed into "Technische Vereinigung der Fabrikanten gummifreier Isolierstoffe e.V." - "Technical Association of Manufacturers of non-rubber insulating materials".

The MPAD molding marks were used until ca.1960. Note that molded material identifier codes made a comeback in 1988, when the Society of the Plastics Industry (founded in the USA in 1937) introduced its Resin Identification Code. It is used worldwide on plastic items, in combination with the universal triangular recycling symbol.

Marks on bakelite parts of a Valvo RV12P4000, an aluminium tube socket, and RV12P200s

The above markings measure 3 - 5 mm in diameter. On other items, e.g., (field)telephones "(Feld)Fernsprecher", they are 5 - 10 mm.

MPAD "56 31,5", "54 *S", "12 42", and "1380" appear on parts of the 1944 Valvo RV12P4000 that I dismantled (the bakelite "Isolierplatte", the 1-hole bakelite disk, the 4-hole bakelite disk, and the 1-hole bakelite disk, respectively). MPAD "56 31,5" also appears on the base of a Valvo RV12P2000 in my collection. It has a WaA745 acceptance stamp and manufacturing date 45/44 H. MPAD "54 *S" also appears on the base of post-war RFT RV12P2000. MPAD "W3 *S" appears on bottom (near the hole and contact for grid pin 7) of the perforated-metal tube socket shown further above.

The 3D/stereoscopic photo below is anaglyphic: you will need a pair of red/green glasses to get the 3D effect. I am not aware of the existence of any other 3D photos (historical or new, like mine) of Hellschreibers and Wehrmacht tubes. If you know of any, please let me know.

RV12P4000 tube with knob removed - capacitor between anode & ground visible
(click on image to get full size)

Like I did for my BF-224F receiver, I have made sure that I have a at least a full set of spare tubes for the Hellschreiber. Got mine at Frag Jan Zuerst / Ask Jan First!, but they are offered regularly (and with widely varying prices) in on-line auctions such as eBay^®.

RV12P4000 tubes were manufactured by several companies: Telefunken, Valvo (Philips), and TeKaDe. These companies have an interesting history, that is intertwined largely due to leveraging of patents. The worldwide light bulb and tube industries were rife with cartels - perfectly legal in most western countries until the mid-1950s - mid-1980s. Ref. 86-90.

The Telefunken history dates back to 1903, when the "Gesellschaft für drahtlose Telegraphie, System Prof. Braun und Siemens & Halske m.b.H." and the "Allgemeine Elektrizitäts-Gesellschaft" (AEG) were instructed by Emperor Wilhelm II to form a joint-venture to pool their patents and efforts. This company was called "Gesellschaft für drahtlose Telegraphie m.b.H." Ref. 91. It had the telegraph address "TELEFUNKEN", which became the company's trademark and later on its name. As the name Telefunken suggests, the main activities were initially related to spark transmitters. Telefunken developed an estimated 75% of all tubes manufactured in Germany up to 1945. Based on its many patents, Telefunken was able to establish a monopolistic position in the tube sector. Telefunken was fully absorbed into AEG in 1966. Ref. 44. Telefunken AG, was one of the the last Western manufacturer of vacuum tubes and ceased production in the mid 1980s. The post-war production volume of their West-German factories totaled some 670 million tubes!

The Radioröhrenfabrik GmbH (RRF) was founded in April of 1924 in Hamburg by C.H.F. Müller AG ("Röntgenmüller"), the sole manufacturer of X-ray tubes in Germany at that time. They also manufactured transmitter tubes and receiver tubes (starting 1916 and 1921 respectively). In 1924, the Müller company ran into financial problems: as part of a (hostile) take-over attempt, Siemens-Halske Co. (!) no longer paid its outstanding bills to them. Max Liebermann, owner of Müller since 1909, enters into a bail-out venture with the Dutch company N.V. Philips Gloeilampenfabrieken in 1925. Philips was also an X-ray tube manufacturer, and eager to get access to the German tube and radio market. That same year, Telefunken, unaware of Philips' link with Müller, enters into an agreement with Philips: Philips could only import a limited number of tubes to Germany, and only via direct sales to Telefunken. In 1926, Telefunken enters into an agreement with Müller/RRF, allowing the latter to produce tubes, and sell them wholesale and retail, but not to equipment manufacturers. The latter were still obliged to buy their tubes only from Telefunken. In 1926, the brand-name "Valvo" is adopted. Liebermann sells Müller and RRF to Philips in May of 1927 (the same year that Philips bought Mullard Radio Valve Co. Ltd in England). Towards the end of 1931, Philips, and its direct competitor Telefunken enter into a formal agreement with world-wide coverage, regarding cross-licensing of patents, sales channels, and tube types; this superseded their 1925 and 1926 agreements. Both Philips and Telefunken had additional agreements with other tube manufacturers (e.g., Lorenz, TeKaDe, Tungsram). They are henceforth called Philips-Valvo Werke GmbH. It is fully absorbed into Deutsche Philips GmbH in 1932. Valvo/Philips also founded the "Studiengesellschaft für Elektronengeräte mbH", short "Studiengesellschaft" (Research Company). It was also located in Hamburg, and specialized in "drift tubes", the predecessor of the klystron. It had rather limited production capacity. May 1951, Philips-Valvo Werke GmbH is renamed to Deutsche Philips GmbH. Valvo ceased to exist in 1975. Philips bought tube manufacturing companies in many countries, e.g., "Radio Technique" and "Dario" in France.

The origins of TeKaDe go back to ca. 1858, when Johann Friedrich Heller opened the first electrical company in Nürnberg: a machine shop for the manufacturing of medical and physics devices, and... door bells. In 1860, his first apprentice was Johann Sigmund Schuckert, who dabbled in telegraphy equipment on the side, and founded "Schuckert & Co. Offene Handelsgesellschaft (OHG)" in 1885. The Schuckertwerke was acquired by Siemens-Halske in 1903, and combined with a Siemens-Halske electrical division to form Siemens-Schuckertwerke GmbH. Heller also expanded his activities to telegraphy equipment, and the company name is changed to "Friedrich Heller, Fabrik Elektrotechnischer Apparate" at the end of 1875. In 1904 the company became insolvent and was bought by Felten & Guillaume in Köln (Cologne), originally a rope making company founded in 1826, later a cable and wire company with a cable factory in Nürnberg. In 1912 Felten & Guillaume combine their operations in Nürnberg into the "Süddeutsche Telefon-Apparate, Kabel- und Draht-Werke A.G." (Southern-German Telephone Devices, Cable & Wire Works). The company has the telegraph address TeKaDe. Until August of 1927, their trademark is TKD (pronounced Te-Ka-De in German). In 1916, TeKaDe started its own tube manufacturing, including "multiple-tubes" ("Mehrfachröhre") for Telefunken. At one point, a patent battle with Telefunken forced TeKaDe t ohalt its tube manufacturing - other than for Telefunken. In the early 1920s, their product range is expanded with broadcast radios, headsets, radio tubes, as well as cables and line amplifiers for the telephone system, etc. During the late 1920s, their overall monthly tube production volume was about 100 thousand. TeKaDe developed and manufactured mechanical TV sets from 1928-1936, and CRT-based ("Braunsche Röhre") TVs from 1937-1938. The tube factory in Nürnberg was bombed in January of 1944, and production was moved to Helmbrechts and Asch (now in the Czech Republic). After the war, TeKaDe made "Ersatz" tubes out of Wehrmachtröhre for a while. In 1949, Philips and Felten & Guillaume founded "Felten & Guilleaume Fernmeldeanlagen-GmbH" (FGF) for telephone equipment, tubes, radios, and car phones. The latter included the "TeKaDe-B72", developed for the Deutsche Bundespost in 1958 for the - at the time - world's largest mobile p hone netweork in the world, the "A-Netz". The phone weighed 16 kg (≈ 35 lbs) and cost about 16k DM. In 1982, FGF was consolidated with other Felten & Guillaume divisions and Philips Data Systems, to form Philips Kommunikationsindustrie AG (PKI), later bought by AT&T.

Besides Telefunken, Valvo/Philips/Studiengesellschaft, and TekADe, there were many other companies involved with development and manufacturing of (specialized) Wehrmachtröhren, e.g. (ref. 16, 84): AEG, Fernseh GmbH (incl. video cameras for remotely controlled bombs and missiles), GEMA ("Gesellschaft für elektroakustische und mechanische Apparate mbH"), Koch & Sterzel (Dresden), Lorenz (Berlin), Loewe/Opta (Berlin), Rectron GmbH (Berlin), Blaupunkt, Sanitas, Siemens & Halske (Berlin, Erlangen, München), Hochohm Gesellschaft ("HOGES"; Berlin), Stabilovolt (Berlin), Funkstrahl-Gesellschaft für Nachrichtentechnik mbH (part of Julius Pintsch Maschinenfabrik und Beleuchtungs-Gesellschaft; Berlin, Konstanz), OSRAM (Berlin; for AEG/Telefunken), Zeiss-Ikon, RPZ (Reichspostzentrale), Flugfunk-Forschungsinstitut Oberpfaffenhofen (FFO; the founder, Prof. Max Dieckman, was graduation professor of Rudolf Hell), and Tungsram (ref. 85). Factories were located in Germany and in German-controlled countries (Austria, Netherlands, Czechoslovakia, Italy,...).

1944 Telefunken advertising in Funk-Technische Monatshefte (FTM, Heft 1, p. 20)

REFERENCES:

	Ref. 1: "Inspection of Philips Works at Eindhoven, September 23-26, 1944", Combined Intelligence Objectives Sub-Committee (CIOS); CIOS file No. III-1 (transcribed and annotated by Arthur Bauer, PA0AOB, cf. website of Foundation for German communication and related technologies)
	Ref. 2: "German World War II communications receivers; Parts I-IV" (Hellschreiber on pp. 1-3), Dick Rollema, PA0SE, CQ Magazine, 8/1980, 12/1980, 5/1981, 8/1981
	Ref. 3: "All You Ever Needed to Know--and Even More--About European Tube-Numbering Schemes", by Martin Faust, DK9QT
	Ref. 4: "Tube number systems", by Frank Philipse
	Ref. 5: "The proliferation of tube types", by Joachim Goerth
	Ref. 6: "Einheitsröhreserie" ("Standardized Tube Series"), by Reinhard Kretzman, Funk-Technische Monatshefte (FTM), Heft 11/12, 1942, pp. 157-160 (from website of Foundation for German communication and related technologies) [in German]
	Ref. 7: "Some hardly known aspects of German military communications during World War Two", by Arthur O. Bauer, lecture at 2008 Autumn Symposium of the Defence Electronics History Society (DEHS), Shrivenham/UK, 16 October 2008, 26 pp. (from website of Foundation for German communication and related technologies)
	Ref. 8: "Die Gegenspieler in Europa: Philips und Telefunken" in "Radio-Katalog 2: Deutschland, Österreich, Schweiz" by Ernst Erb, April 2006, 400 pp., ISBN-10: 3881806520 [in German]
	Ref. 9: "Wehrmachtsröhren Farbcodierung" [in German]
	Ref. 10: "RV12 P 4000 - Technische Daten und Streuwerte", Telefunken data sheet G.R.B. 12 D II (5000), 2 pp. Based on the square Telefunken logo used in this document, it was published after mid-1937.
	Ref. 11: "Wehrmachtröhren", Telefunken data sheet C.R.B. 29 D VII (4000), September 1944, 4 pp.
	Ref. 12: "25 Jahre Valvo-Röhren", Funkschau, Vol. 21, 1949, Heft 5, p. 77
	Ref. 13: "Röhrenfarben der Wehrmacht", Museum für historische Wehrtechnik e.V.
	Ref . 14: "Röhrenhistorie 1: Zeitgeschichte - Technologie - Codierung - Lexicon", Wolfgang Scharschmidt, Funk Verlag Bernhard Hein e.K., 616 pp., ISBN: 3-936318-70-0 [click here for a 7 page extract on the publishers website]
	Ref. 15: "Röhrenhistorie 2: Firmenporträts", Wolfgang Scharschmidt, Funk Verlag Bernhard Hein e.K., 600 pp., ISBN: 978-3-939197-29-4 [click here for a 4 page extract on the publishers website]
	Ref. 16: "Röhrenhistorie 4: Deutsche Wehrmachtsröhren", Wolfgang Scharschmidt, Funk Verlag Bernhard Hein e.K., 360 pp., ISBN: 978-3-939197-31-7 [in German] - to be published 2010 [click here for a 7 page extract on the publishers website]
	Ref. 17: "Röhrenhistorie 5: Brands - Signets - Technische Daten", Wolfgang Scharschmidt, Funk Verlag Bernhard Hein e.K., 440 pp., ISBN: 978-3-939197-32-4 - to be published 2010
	Ref. 18: "Zur Geschichte der RV 12 P 2000 - ein nostalgischer Rückblick auf eine legendäre Röhre“, Volume 4 of "Schriftenreihe zur Funkgeschichte“, Gerhard B. Salzmann, Gesellschaft der Freunde der Geschichte des Funkwesens (Ulm, Germany), Walz Verlag, 1994, 88 pp., ISBN/ISSN: 3-9802576-2-2
	Ref. 19: "Kunstharzpressstoffe und andere Kunststoffe: Eigenschaften, Verarbeitung und Anwendung", Walter Mehdorn, Springer Verlag, 3rd ed., 1949, 354 pp., ASIN: B0000BLFXN. The 1938 listing of Kunststoffkenzeichen is here.
	Ref. 20:"Aus der Rüstung des Dritten Reiches: das Heereswaffenamt 1938-1945; ein authentischer Bericht des letzten Chefs des Heereswaffenamtes“, Emil Leeb, Wehrtechnische Monatshefte (Zeitschrift für Wehrtechnik, Wehrindustrie und Wehrwirtschaft, Deutschen Gesellschaft für Wehrtechnik), Volume 4, 1958, Beiheft, 76 pp.
	Ref. 21: "Spezial- und Wehrmachtsröhren, UKW-Röhren (λ = 10 - 1 m)", Gerhard Bogner, Folge 6 of Teil 6 "Zeitraum 1934-1940" of "Entwicklung des UKW-Rundfunks", Funkgeschichte (Gesellschaft der Freunde der Geschichte des Funkwesens (GFGF) e.V.), Nr. 141/2002
	Ref. 22: "Problematik und Entwicklungsbeginn von UKW-Empfängerröhren", Gerhard Bogner, Folge 3 of Teil 6 "Zeitraum 1934-1940" of "Entwicklung des UKW-Rundfunks", Funkgeschichte , Nr. 141/2002
	Ref. 23: "Introduction to the Radio Valve", F. Langford-Smith, chapter 1 (pp. 1-12) of part 1 of "Radiotron Designers Handbook", Radio Corporation of America (RCA), 4^th ed., 1952, 1482 pp.
	Ref. 24: "Development and Production of the New Miniature Battery Tubes", N.R. Smith, A.H. Schooley, RCA Review, April, 1940 (also: pp. 375-381 in ref. 67.
	Ref. 25: "Technical Problems in the Construction of Radio Valves", Th. P. Tromp, Philips Technical Review, Vol. 6, Nr. 11, November 1941, pp. 317-323
	Ref. 26: “Microwave tube development in Germany from 1920-1945”, H. Döring, International Journal of Electronics, Volume 70, Issue 5, May 1991, pages 955 – 978“ (original German version of this paper appeared in "Frequenz", nr. 43, 1989, pp. 277–283 and 309–314)
	Ref. 27: "Das Heereswaffenamt", Claus Espeholt, December 2009
	Ref. 28: “Elektronenröhren für Panzerfunkgeräte”, Chapter 22.2.4 in “Funk- und Bordsprechanlagen in Panzerfahrzeugen“, Band 3 of “Die deutschen Funknachrichtenanlagen bis 1945”, H.-J. Ellisen, Marketing & Technik Verlag, 1991, 240 pp., ISBN 3928388010
	Ref. 29: “RV 12 P 2000 und andere Spezialröhren als Ersatz für normale Radioröhren und für den Neuaufbau von Empfangsgeräten/Neubauschaltungen mit Selen-Gleichrichter“, Günter Heine, Rudolf Wollenschläger, Deutscher Funk-Verlag, Berlin, 1946, Heft Nr. ??, 19 pp.; 1996 reprint Freundlieb Verlag Historischer Technikerliteratur
	Ref. 30: "Grondslagen van de Radiobuizentechniek, 1e deel", J. Deketh, Meulenhof Publ. , 1943, 528 pp.
	Ref. 31: "Die RV12 P 2000 - Story", Joachim Gittel, 2008
	Ref. 32: "The Story of the Valve", C. H. Gardner, Radio Constructor, 1965, Data Publications
	Ref. 33: "Die universelle Verwendbarkeit von kommerziellen Röhren", H. Zimmerman, Hamburger Funk-Technik für den Fachmann und den Bastler, Sonderdruck Nr. 2011, Hamburg, June 1947, 4 pp. (von der Militärregierung genehmigt - published with permission of the military government!)
	Ref. 34: "Guten Empfang bringt die BASTELFREUND-Schaltung", "Bastelfunk - Schaltung 112: Einkreis - 4- Röhrenempfänger für Gleich-, Wechsel-, und Batteriestrom" (Sept. 1940, 4x RV2,4P700, "Bastelfunk - Schaltung 119: Zweikreis - 4- Röhrenempfänger für Allstrom" (3x RV12P2000), "Bastelfunk - Schaltung 120: Zweikreis - 4 - Röhrenempfänger für Allstrom" (3x RV12P2000), Alexander Frentzel, München.
	Ref. 35: "Preßglas-Röhren", Reinhard Kretzmann, Funktechnische Monatshefte (FTM), Heft 10, 1941, pp. 156-159.
	Ref. 36: “Reliability in Miniature and Sub-Miniature Tubes”, P.T. Weeks, Proc. of the Institute of Radio Engineers (IRE), May 1951, pp. 499-503
	Ref. 37: “The Design and Development of Three New Ultra-High-Frequency Transmitting Tubes”, C.E. Haller, Proc. of the Institute of Radio Engineers (IRE), January 1942, pp. 20-26
	Ref. 38: "The RCA Radiotron Manual", RCA Technical Series No. R-10, RCA Radiotron Co., Inc., 1932 (1937?), 87 pp.
	Ref. 39: "Universalröhre: RV 12 P 2000 Kennzeichnung, Bauform, Bauartänderung im Laufe der Entwicklung als Vorkriegs-, Kriegs- und Nachkriegsausführung", Gerhard B. Salzmann, 1997
	Ref. 40: "RV 12 P 2000 HF-Pentode Technische Daten und Streuwerte", Telefunken data sheet G.R.B. 3 D (5000), 2 pp. Based on the square Telefunken logo used in this document, it was published after mid-1937.
	Ref. 41: "NF4 HF-Pentode Technische Daten und Streuwerte", Telefunken data sheet G.R.B. 7 D (5000), 2 pp. Based on the square Telefunken logo used in this document, it was published after mid-1937.
	Ref. 42: "RL 2 P 3 Pentode für Enstufen u. Sendezwecken Technische Daten", Telefunken data sheet G.R.B. 5 D II (5000), 2 pp. Based on the square Telefunken logo used in this document, it was published after mid-1937.
	Ref. 43: "RV 2 P 800 HF-Pentode Technische Daten und Streuwerte", Telefunken data sheet G.R.B. 11 D II (5000), 2 pp. Based on the square Telefunken logo used in this document, it was published after mid-1937.
	Ref. 44: "25 Jahre Telefunken 1903 – 1928; Festschrift der Telefunken-Gesellschaft", Fritz Schröter, Ernst Zechel, Otto Nairz (editors), Berlin, 1928, 328 pp.
	Ref. 45: "Das Königliche Materialprüfungsamt der Technischen Hochschule Berlin auf dem Gelände der Domäne Dahlem beim Bahnhof Groß-Lichterfelde West – Denkschrift zur Eröffnung", Adolf Martens, Manfred Guth, Julius Springer Verlag, Berlin, 1904, 380 pp.
	Ref. 46: "Bakelite - Seine herstellung und Verwendung" [Bakelite, its manufacture and application], Bakelite Gesellschaft mbH, document 668/3537/Wbr, 1937, 44 pp.
	Ref. 47: "Moulding bakelite materials: the design, production, and use of moulds for synthetic resin compounds", Volume 3 of Machinery's yellow-back series, Machinery Publishing Co., Ltd., 2nd ed., 1942, 62 pp.
	Ref. 48: Normblatt DIN 7701 "Kunstharz-Preßstoffe, warmgepreßt" [hot-moulded synthetic plastics)],1936; Issue 2, 1938 "Kunstharzpreßstoffe, Kunsstoffe" [molded synthetic resin, plastics]
	Ref. 49: "Deutsche Fertigungskennzeichen bis 1945“, Michael Heidler, Vogt-Schild Deutschland, 2007, 506 pp, ISBN/ISSN: 3-9811018-5-5; Signatur: 2000/Gesch. 777.881
	Ref. 50: "Liste der Fertigungskennzeichen für Waffen, Munition und Gerät“, Pawlas Verlag, 1977, 782 pp.
	Ref. 51: "Das Heereswaffenamt und die KWG im "Drittem Reich" - die militärischen Forschungsbeziehungen zwischen 1918 und 1945", Burghard Ciesla, pp. 32-76 in "Gemeinschaftsforschung, Bevollmächtigte und der Wissenschafttransfer - Die Rolle der Kaiser-Wilhelm-Gesellschaft im System kriegsrelevanter Forschung des Nationalsozialismus", Helmut Maier (ed.), Wallstein Verlag, 2007, 613 pp., ISBN-10: 3835301829
	Ref. 52: Section II "System of Supply within Germany" and Section III "System of Supply of the Field Army" of Chaper VI "Supply, Evacuation, and Movements" in "Handbook on German Military Forces", U. S. War Department Technical Manual TM-E 30-451, 15 March 1945; reprinted by Louisiana State University Press, 1995, 670 pp., ISBN-10: 0807120111
	Ref. 53:"Das große Röhren-Handbuch", Ludwig Ratheiser, Franzis Verlag GmbH, 1995 (reprint of 1955 ed.), 296 pp, ISBN: 377235064X
	Ref. 54:"Zur Entstehung der elektronischen Technologie in Deutschland und den USA. Der Beginn der Massenproduktion von Elektronenröhren 1912-1918", Hartmut Petzold, in "Sozialgeschichte der Technik", Vol. 13 (1987), Nr.3, pp. 340-367 of "Geschichte und Gesellschaft - Zeitschrift für historische Sozialwissenschaft", Vandenhoeck & Ruprecht Publ.
	Ref. 55: "Funkschau-Tabelle der Wehrmachtröhren“, Ludwig Ratheiser, Funkschau-Verlag, München, 1944, 39 pp., 1. ed., 1944; also in ref. 56
	Ref. 56: “Handbuch der Wehrmachtröhren", Werner Gierlach (DL6GW), Verlag Walter de Gruyter, Berlin
	Ref. 57: "7 erprobte Schaltungen. Für den erfahrenen Bastler zum Selbstbau unter Verwendung von Spezialröhren. Der Rundfunk-Bastler", Richard Grüneberg, Deutscher Funk-Verlag GmbH Berlin, Issue A, 1946, 149 pp; Issue B, new and expanded edition, 1947, 27 pp.
	Ref. 58: "Abkürzungen", p. 5 in "Dienstanweisung für die Bauaufsichten (BAL) des Reichsluftfahrtministeriums. Teil 1: Aufgabengebiet", Luftdienstvorschrift L.Dv. 61/1, 1 August 1940, 65 pp.
	Ref. 59: "Die MAN: eine deutsche Industriegeschichte“, Johannes Bähr, Ralf Banken, Thomas Flemming, 2008, C.H. Beck Publ., 544 pp., ISBN-10: 3406577628
	Ref. 60: "Elektronenröhre", Section 3.2.1. in "Blitz und Anker, Band 1: Informationstechnik - Geschichte und Hintergründe", Joachim Beck, August 2005, Books on Demand GmbH, 560 pp., ISBN: 3833429968
	Ref. 61: "Zur Entstehung der elektronischen Technologie in Deutschland und den USA. Der Beginn der Massenproduktion von Elektronenröhren 1912-1918", Hartmut Petzold, in "Sozialgeschichte der Technik", Vol. 13 (1987), Nr. 3, pp. 340-367 of "Geschichte und Gesellschaft - Zeitschrift für historische Sozialwissenschaft", Vandenhoeck & Ruprecht Publ.
	Ref. 62: "Philips in Hamburg", July 2008, 2 pp.
	Ref. 63: "BA-, BAL-, Wa.A.- und W.ab-Stempel auf Röhren", Werner Thote, discussion tread in the Forum of Radiomuseum.org, March 2008 - January 2009
	Ref. 64: "Massenproduktion im globalen Kartell - Glühlampen, Radioröhren und die Rationalisierung der Elektroindustrie bis 1945“, Günther Luxbacher, Verlag für Geschichte der Naturwissenschaften und der Technik, 2003, 490 pp., ISBN 978-3-928186-68-1
	Ref. 65: "Röhrencodierungen der 20er und 30er Jahre", Gerhard Salzmann, Vol. 1 of "Schriftenreihe zur Funkgeschichte", Gesellschaft der Freunde der Geschichte des Funkwesens (GFGF e.V.), 1988, Winkler Verlag, 191 pp. ISBN 3-924517-25-8
	Ref. 66: "Recent developments in miniature tubes", Salzberg, B., Burnside, D.G., Proc. of the Institute of Radio Engineers (IRE), Vol. 23, Issue 10, October 1935, pp. 1142-1157; also published as pp. 292-307 in ref. 67
	Ref. 67: "Electron Tubes - Volume I (1935-1941)", Goldsmith, A.N., Van Dyk, A.F., Burnap, A.S., Dickey, E.T., Baker, G.M. (eds.), RCA, March 1949, 483 pp.
	Ref. 68: "Die Telefunkenröhren und ihre Geschichte", Rukop, H., pp. 114-154 in ref. 44
	Ref. 69: "Rückblick auf die Spezialröhrenentwicklung der deutschen Funkmess- und Dezimeter-Wellentechnik", Müller, O., Frequenz, Vol. 16, 1962, pp. 294-308
	Ref. 70: “Enigma", [incl. PA0AOB Hellschreiber] D.W. Rollema (PA0SE), Wireless World, Vol. 89, Nr. 1569, June 1983, p. 49-54
	Ref. 71: "The Tiltman Break", F.L. Bauer, Appendix 5, pp. 370, 371 in "Colossus: the secrets of Bletchley Park's codebraking computers", B. Jack Copeland (ed.), Oxford University Press, 2006, ISBN 019284055X, 462 pp.
	Ref. 72: "Die Geschichte der Hörhilfen", Was sie wurden, was sie sind“, Aubrey Miller, Hörakustik, Nr. 5, May 1995, Median-Verlag, Heidelberg
	Ref. 73: p. 287. in "Bekanntmachung der Abteilung Post- und Fernmeldewesen der Provinzialverwaltung Sachsen", VOBI PS, 2 (1946), Nr. 28, 6 July 1946; referenced on p. 142 in "Zensur und Zensoren - Medienkontrolle und Propagandapolitik unter sowjetischer Besatzungsherrschaft in Deutschland", Strunk, P., Akademie Verlag, 1996, 183 pp., ISBN 978-3-05-002850-71996.
	Ref. 74: "Manufacture of valves by machinery", Hall, T.F.B., How, A.H., J. of Scientific Instruments, Vol. 16, Nr. 9, September 1939, pp. 277-285
	Ref. 75: "Vacuum Sealing Techniques", Roth, A., American Institute of Physics Publ., 1997, 860 pp. , ISBN-10: 1563962594
	Ref. 76: "Theory and Operating Characteristics of the Thermionic Amplifier", H.J. van der Bijl, Proc. of the Institute of Radio Engineers (IRE), Vol. 17, April 1919, pp. 97-128; reprinted in Proc. of the IEEE, Vol. 86, No. 12, December 1998, pp. 2455- 2467
	Ref. 77: "The Remarkable Dr. Hendrik van der Bijl", D.J. Vermeulen, Proc. of the IEEE, Vol. 86, No. 12, December 1998, pp. 2445-2454
	Ref. 78: "GEMA: birthplace of German radar and sonar", Harry von Kroge, Taylor & Francis Publ., 2000, 206 pp., ISBN 0750307323; (English translation of the book "GEMA-Berlin, Geburtsstätte der deutschen aktiven Wasserschall- und Funkortungstechnik", 1988)
	Ref. 79: "A new principle of construction for radio valves", P.C. Cath, Philips Technical Review, Vol.1, No.6, 1939, pp.162-166
	Ref. 80: "A New All-Glass Valve Construction", F. Prakke, J.L.H. Jonker, M.J.O. Strutt, The Wireless Engineer, May 1939
	Ref. 81: "The gyrator, a new electric network element", B. D. H. Tellegen, Philips Research Reports, Vol. 3, No. 2, Apr 1948, pp. 81-101
	Ref. 82:"Aus der Rüstung des Dritten Reiches: das Heereswaffenamt 1938-1945; ein authentischer Bericht des letzten Chefs des Heereswaffenamtes“, Emil Leeb, Wehrtechnische Monatshefte (Zeitschrift für Wehrtechnik, Wehrindustrie und Wehrwirtschaft, Deutschen Gesellschaft für Wehrtechnik), Volume 4, 1958, Beiheft, 76 pp.
	Ref. 83: "Das Heereswaffenamt", Claus Espeholt, December 2009
	Ref. 84: "Wehrmacht-Röhren" website by H.-T. Schmidt, including "Farbcode der Wehrmachtröhren" (color coding) [in German]
	Ref. 85: "Tungsram’s positioning strategies on the world market in the interwar period - Why not Europe? Sources of economic growth", Mária Hidvégi, European Science Foundation / GlobalEuroNet, Summer School 2007
	Ref. 86: "Massenproduktion im globalen Kartell - Glühlampen, Radioröhren und die Rationalisierung der Elektroindustrie bis 1945", Günther Luxbacher, GNT-Verlag, 2003, 490 pp., ISBN 978-3-928186-68-1
	Ref. 87:"Die Gegenspieler in Europa: Philips und Telefunken", in "Radiokatalog - Band 2: Deutschland, Österreich, Schweiz", Ernst Erb, Verlag für Technik, 2006, 400 pages
	Ref. 88: “Transnational Corporations in Electrical Industry”, Economic and Political Weekly, Vol. 14, No. 3 (Jan. 20, 1979), pp. 103, 105-106
	Ref. 89: "Die internationale Stellung Telefunkens", Carl Schapira, pp. 52-59 in: "25 Jahre Telefunken 1903 – 1928; Festschrift der Telefunken-Gesellschaft", Fritz Schröter, Ernst Zechel, Otto Nairz (editors), Berlin, 1928, 328 pp.
	Ref. 90: "Webs of Power - International Cartels and the World Economy", Kurt Rudolf Mirow, Harry Mauerer, Houghton Mifflin Harcourt Publishing Company, 1982, 525 pp., ISBN 0395305365
	Ref. 91: "Marksteine der Telefunken-Entwicklung von 1903 bis 1945", Telefunken-Zeitung, 23. Jg., Heft 87/88, September 1950, pp. 5-8
	Ref. 92: "40 Jahre VALVO - Empfängerröhren", in "Valvo Berichte", Band X, Heft 1/2, Sonderheft zum vierzigjährigen Firmenjubiläum, April 1964, 292 pp.

Links:

"German military tubes1933-1945 and World war II" page of Wumpus's Old Radio World

"Tube collection" by Udo Radke

"Elektronenröhre", Wipedia article in German [here in pdf]

The National Valve Museum (virtual museum, lots of documentation).

Many of the classical books on vacuum tube theory & circuit design can be downloaded here (only books with expired copyrights, so: for free!)

	23-June - 7-July-2010: expanded text on Waffenamt stamps and other markings.
	4-June-2010: added photos of all tube parts + text + 3D photos; added separate page for photos and notes on all my RV12P4000 tubes; added refs. 24-48.
	9-May-2010: expanded text; added TeKaDe knob picture.
	30-March-2010: added picture of tube socket and markings; expanded text on WaA and BAL stamps.

	Tube characteristics and performance were sensitive to temperature, vibration and shock, as well as to variations in filament voltage.
	Seating of the tubes in their sockets was unreliable.
	They were too big.
	They were not easy to replace in situ.
	Replacement of tubes impacted the function and performance of the equipment (frequency, power, amplification, sensitivity).
	There was too much variability of the electrical characteristics of same-type tubes.
	The upper limit of the operating frequency was low.
	Unreliable for orientation other than upright.

	R: "Reichsheer" = Army, or "Reichswehr" = Army/Navy
	V: "Empfangs-Verstärkerröhre" = receiver amplifier tube
	12: average heater voltage
	P: type = pentode
	4000 = (static) amplification factor μ

	Grundig Radio-Werke G.m.b.H. in Fürth/Bavaria (Radio-Vertrieb, RVF Elektrotechnische Fabrik G.m.b.H.): "Heinzelmann Model A" (Long Wave (LW), Medeium Wave (MW), Short Wave (SW); RV12P2000/2001 + RV12P2000/2002). This was a small, inexpensive kit that was sold without the required tubes. This way, Grundig cleverly bypassed both the ban by the allied military government on the manufacturing of radio sets ("A radio without tubes is not a radio - but a toy"), and the ration-coupon based economy of that time.
	Blaupunkt-Werke GmbH in Berlin: model 5GW646 (LW + MW + SW, 5x RV12P2000, 2x RV12P2001, 1946-1947). Blaupunkt (Ideal) was part of Robert Bosch GmbH, Stuttgart. In 1929, Bosch founded the Fernseh AG, together with Baird Television Ltd., Radio AG D.S. Loewe, and Zeiss Ikon AG. Since 1932, and to this day, Blaupunkt makes car radios.
	Sachsenwerk in Radeberg: model 463W (LW + MW; incl. 2x RV12P4000, 1946-1947).
	G. Schaub Apparatebau-Gesellschaft mbH in Pforzheim: model 2K-47 (LW + MW; 3x RV2P2000, 1947-1949; C. Lorenz AG took over Schaub in 1940, on government orders).
	Lembeck & Co. Gerätebau und Vertriebsgesellschaft (Lembeck-Radio) in Braunschweig: model L147W (LW + MW + SW, 3x RV12P4000,1947-1949). Lembeck produced communications equipment for the Wehrmacht during WWII, and built radios until 1954.
	Atlas-Werke AG in Bremen and Munich: model Ra2 (MW + KW, 3x RV2P2000, 1947-1948). Atlas was involved with shipbuilding (incl. U-Boats and minesweepers), and related equipment such as depth gauges, active and passive sonar. Their Maschinenfabrik manufactured parts of the famous Enigma encryption system (also ref. 70, 71). One of their sonar systems built in Bremen comprised 52 tubes of type RV12P200. Their stock was used after the war for the Ra2, built at their factory in München. The same tube was also used in a tabletop model hearing aid that Atlas sold 1946-1948 (ref. 72).
	Telephon- und Telegraphenfabriks-AG Kapsch & Söhne in Vienna/Austria: model 247G and 248B (MW, 2x RV12P800, 1947)
	Signalbau AG, Dr. Erich F. Huth ("Huth Signalbau AG") in Berlin and Hannover: model 12P (LW + SW; 5x RV2P2000, 1945-1946). During the 1920s, Telefunken and Lorenz became major shareholders of Huth. Model 12P was built in Hannover for Lorenz. Huth was also a small tube manufacturer.

	The end of a section of glass tubing is heated while being spun.
	A wide cone is inserted into the soft end of this tube, to create a flange ("flare") with the diameter of the final vacuum tube.
	The lead-in wires are placed into a jig, to hold them into position.
	The wires are then inserted into and through the flanged tube.
	A small glass tube is inserted between the wires (for later attachment of a vacuum pump).
	The entire assembly is heated until soft.
	Metal jaws squeeze the molten glass around the wires, to fuse them.
	Air is blown into the small tube, to create a hole through the stem.

	10 W.S.h: 10 Watt AM/CW Wehrmacht transmitter, 25-27 MHz , 1x RV12P4000, ca. 1939.
	MS3a: Hell Schnellmorseschreiber, 2x RV12P400, 1939.
	Fprüf.b: frequency tester ("Frequenzprüfgerät") for receivers and transmitters, 25 - 48 MHz; 1x RV12P4000, 1936.

	The tube's electrodes are spot-welded to the lead-in wires at the top of the pinch-stem. The electrodes sub-assembly, with mica spacers - if necessary, is also referred to as the "system". The combined stem plus system is called the "mount".
	The mount is inserted into the tube's glass envelope ("vessel", "globe"; D: "Kolbe") until the flange of the stem touches the tube. A grid wire may stick out of the top.
	While turning, the tube's edge is fused to the flange of the glass stem.
	While turning, the top of the the tube heated until it forms the dome shaped top of the top. The small protrusion where the dome is closed is called the "nub".
	The tube is evacuated via the small glass tube in the stem, which is then melted shut.
	The lead-in wires are connected to the pins of the base (D: "Sockel"), and the base is fixed to the tube.

	"The manufacture of radio valves", a Philips-Mullard film; here is part 1, part 2, and part 3 in MP4 format.
	"The manufacture of modern radio valves at the OSRAM - G.E.C. works, London 1930"; here is part 1, part 2, and part 3 in MP4 format.
	"How it is made - vacuum tubes", based on Sylvania material; here it is in MP4 format.
	"Fabrication d'une lampe triode"; here it is in MP4 format. This great 15-minute video shows how Claude (F2FO) makes his own triodes in (he has used them in transceivers to make CW contacts around the world).
	"Glass blowing for vacuum devices" videos shows how to make your own incandescent light bulb, diode tube, etc.

	tube type-designator (here: RV12P4000)
	manufacturing location
	manufacturing date
	acceptance agency
	acceptance date
	"property of"
	other

	WaA 89 is an Abnahmestelle at the Telefunken Röhren- und Gerätewerk in Erfurt, a tube factory founded in 1936. Erfurt is in former East-Germany, and after WWII, this factory became the state-owned VEB RFT Funkwerk Erfurt. The "89" stamp was used from 1943-1945 (cf. pp. 42-43 in ref. 18).
	WaA 338 is a central Abnahmestelle in Berlin. It appears to have only been used in 1936-1937, and for a variety of goods from several manufacturers of radio related equipment. It is very unusal to find it on tubes, such as my Telefunken RV12P4000s.
	WaA 617 also refers to an Abnahmestelle at the Telefunken Röhren- und Gerätewerk in Erfurt. It appears to have been used during the period 1940-1943.
	WaA 745 is the Heeresabnahmestelle at the Valvo tube factory (Röhrenwerk) in Hamburg. It was used during the period 1939 through early April 1945 on tubes manufactured by Valvo/Philips, and the Studiengesellschaft für Elektronengeräte mbH. The Studiengesellschaft was an R&D and prototyping lab in Hamburg with a a small production capability. It was founded by Valvo/Philips in 1939 and developed special tubes such as "drift tubes", the predecessor of the klystron.
	WaA 836 is a general Abnahmestelle in Nürnberg. It was used tubes from the Süddeutsche Telefon-Apparate, Kabel- und Draht-Werke A.-G. (TeKaDe, frmr. TKD). WaA 836 is also used from 1943-1944 on electrical and electronic products from regional companies such as AEG, Nürnberger Schraubenfabrik und Elektrowerk (N.S.F; the electrical part of the company merged with AEG in 1942), Lumophon (radios, telephones; acquired by Grundig in 1951), and Kabel- und Metallwerke Neumeyer AG. The latter was part of the Gutehoffnungshütte Aktienverein für Bergbau und Hüttenbetrieb (GHH) conglomerate, that also included large companies such as Maschinenfabrik Augsburg Nürnberg AG (M.A.N.). See ref. 59. M.AN. and Krupp financed the ultimate development by Rudolf Diesel his invention: the "rotational heat engine" that bears his name.

	Wehrmachteigentum
	Wehrm.-Eigentum
	Wehrmacht
	Wehrm.
	Heereseigentum
	Heereseigent.
	R.L.M. Eigentum
	RLM Eigentum
	Eigentum RLM
	Kriegsmarine

	54: refers to Ellinger und Geissler Fabrik Elektrotechnischer Bedarfsartikel in Dorfhain (Dresden-Tharandt). Incidentally, Dorfhain is also the birthplace of Hermann Mende, founder of Radio-Mende in Dresden. Ellinger & Geissler was a manufacturer of fixed and variable resistors, switches, and tube sockets. They produced bakelite under the trade name Elgesit.
	56: refers to H. Mende und Co. in Dresden, who used the trade name Mendelith for bakelite.
	W3: is Dralowidwerk der Steatit-Magnesia AG, in Berlin-Teltow (see advertising below)

	S: as stated above, this is "Phenolharz mit Holzmehl als Füllstoff", i.e., moldable phenolic resin that is reinforced with sawdust filler., and is usually referred to as "bakelite".
	to the left of the "S": significance unknown
	31,5: ??? does not appear on the 1938 list of Kunststoffzeichen/Pressmarken (ref. 19), but does appear on the 1954 list. Probably bakelite.

	"12 42": significance unknown; the tube in question has 1944 date codes 11/4 and 13/4.
	"1380": significance unknown

	"German military tubes1933-1945 and World war II" page of Wumpus's Old Radio World
	"Tube collection" by Udo Radke
	"Elektronenröhre", Wipedia article in German [here in pdf]
	The National Valve Museum (virtual museum, lots of documentation).
	Many of the classical books on vacuum tube theory & circuit design can be downloaded here (only books with expired copyrights, so: for free!)

	"47/43" and "15.11.43"
	"12. Juli 1937" and "27/37"