There has been a number of Hellschreiber types and models produced under the HELL and Siemens-Halske names, other than the Feld-Hell, Hell 72 GL, and Hell-80 discussed elsewhere on this website. Below is an attempt to provide a description (with varying levels of detail) of those that apply the spindle-principle. Note that this is a work in progress, and may never be an exhaustive list. If you have any additional information or documentation that would be appropriate for this particular page, please contact me.

Note that all major teleprinter manufacturers (e.g., Siemens, Lorenz, Creed, Morkrum-Kleinschmidt/Teleteype) produced teleprinters that print on paper tape, but that are not Hellschreibers. However, some did develop and manufacture Hellschreibers. They are discussed on my "Other Manufacturers" page.

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  Most recent updates on this page:

	8-June-2010: added Blattschreiber ref. 7 and 8.
	3-May-2010: corrected & expanded description of the Blattschreiber, added photos.
	11-Apr-2010: added T empf 14 schematic; moved Hell radio receivers to separate page.
	6-Mar-2010: started sections for Blattschreiber and HE-5/HE-6; expanded info on TFK Presse Hell radios; added Hell patent for optical scan of perforated paper tape on which text is typed with special typewriter.
	27-Feb-2010: added T empf 39d, T empf 44c/e, and T send 62a.
	1-Jan-2010: added schematic Telefunken Presse-Hell receiver E 11.
	17-Dec-2009: added ref. 3, expanded T empf 14 text, added ZETFAX references..
	18-Nov-2009: expanded T empf 14 text.
	31-Oct-2009: added info on Presse-Hell receivers, added refs and images of Bernhardine/Fug120.
	22-Sept-2009: added T empf 14 picture.

    

    

 

 

 

[1929 printer prototype]    [T empf 12]     [T empf 14]    [T send 17]     [T send 18]    [T empf 39d "L"]

[T empf 40 "F"]       [T empf  44 ]     [T send 62 "S"]    [Blattschreiber]     [HE-5 and HE-6]

[FuG 120 "Bernhardine"]         [ZETFAX] 

 

1929 prototype with (electrochemical) printing on chemically impregnated paper tape
(figure 2 in ref 1.)

	Ref. 1: "Die Entwicklung des Hell-Schreibers" by the inventor himself: Rudolf Hell; pp. 2-11 in "Gerätentwicklungen aus den Jahren 1929-1939", in "Hell - Technische Mitteilungen der Firma Dr.-Ing. Rudolf Hell", Nr. 1, Mai 1940   [in German].
	Ref. 2: "Stand der Siemens-Hell-Fernschreibtechnik", R. Zimmerman, Siemens & Halske A.G., Siemens Fernmelde Technik, SH 7997. 0,5. 1043. TT1.  M/1401 (1940?), courtesy Siemens Corporate Archives, München.

Left to right: receiver, amplifier, and "Hell-Siemens" teleprinter
(source: ref. 3)

Ref. 3: "Voici "des machines à écrire" pour télégraphier soi-même de son domicile" [machines for teleprinting yourself at home], Paul Lucas, La Science et la Vie, No. 209, November 1934, pp. 406-410.    new

If you have any information or documentation on this model, please contact me!

The "Presse Hell" model was developed ca. 1935. It was used extensively by press agencies and the German postal system. It measures 31x23x21 cm (≈12x8x9½") and weighs 6½ kg (≈14 lbs). Originally, the housing was made of metal, later it was molded ("Preßstofgehäuse"). It is equipped with a “universal motor”, i.e., an AC series-motor (a.k.a AC commutator motor). Such motors can operate on both DC and single-phase-AC current. Operation is selectable between 125/220 Vac and 110/220 Vdc. The motor has a centrifugal speed regulator, and EMI suppression from 37.5 kHz – 30 MHz.

The T empf 14 is a printer-only! It does not contain any circuitry for a tone-detector or a driver amplifier for the printer solenoid. See Ref. 5. You cannot simply hook it up to the loudspeaker output of a receiver. A "Zwischengerät" must be placed between the printer and regular receiver, or a special "Hellempfänger" (Hell-receiver) with built-in detector and driver must be used. See the Minerva and Telefunken Hell-receivers. About half of the T empf 14 circuitry is for remote on/off control.

Siemens-Hell-Schreiber T empf 14 - front
(source: figure 11 in ref. 2 above)

Siemens-Hell-Schreiber T empf 14 - opened rear with circuit card
(source: figure 4 in ref. 4)

	Ref. 4: “Der neue Siemens-Hell-Schreiber“, Wilhelm Heller, Technische Mitteilungen des Fernmeldewerks, Abt. F. Telegrafengerät, May 1940, Siemens & Halske A. G., Wernerwerk, SH7996, 1.8.40 T T1., 4 pp. (courtesy Siemens Corporate Archives, München)
	Ref. 5: "T empf 14 Schaltplan" [schematic] (courtesy Heinz Blumberg, DC4GL)

This is a keyboard + character drum unit, without printer. If you have any information or documentation on this model, please contact me!

This is a keyboard + character drum unit, without printer. If you have any information or documentation on this model, please contact me!

The T empf 39d (a.k.a. model "L") dates from the early -mid1950s. It is a printer-only model, used to print out messages sent with a Siemens-Hell-Schreiber "GL" ("72") or "AGL" ("73"). Hence, it operates in the start-stop (synchronous) mode, with either 1000 Hz or 3000 Hz tone pulses (selectable).

I need a photo of this model

CHARACTERISTICS (source: p. 26 in ref. 8):

	Width of printed text (12 columns): 2.5 mm
	Width of printed text with space: 3 mm
	Width of paper tape: 9.5 mm
	Printing speed: 6.1 characters/sec (300 Bd)
	Paper consumption (max speed, continuous printing): 1.1 m/min
	Apparent input impedance: 600 ohm
	Minimum input signal level: - 3.5 Neper (-30 dB) at 600 ohm
	Power input: 220 Vac (40-60 Hz)
	Power dissipation: ca. 50 VA
	Fuses: 500 mA and 250 mA (amplifier)
	Motor dissipation: 25 W
	Motor speed (regulated): 2100 rpm
	Tone filter: 1000/3000 Hz (selectable)
	Amplifier tube (valve): EF80
	Keying tube: EL83
	Size: 32x26x20 cm (WxDxH, ≈12¾ x 10¼ x 8")
	Weight: ca. 11 kg (≈24.3 lbs

The start-stop synchronization accommodates up to 2% speed difference between sender and receiver/printer. The motor is a brushless DC type. Its speed regulator is based on a 125 Hz tuning fork. A strobe disk allows visual checking of the speed. The unit has an output (marked "Mh" = "Mithören") for a 4000 ohm headset. The unit responds to a remote control start command: a pulse of at least 180 msec (1 sec typ.) of 25 Hz, 1000Hz, 3000 Hz, or DC. The remote stop command is a 4 sec (min, 6 sec typ.) pulse.

Ref. 6: "Siemens-Hell-Schreiber "L" - T empf 39 d", Siemens Fernschreib Technik, Siemens & Halske AG, Wernerwerk für Telegrafen- und Signaltechnik, Beschreibung St Bs 1223/11 [incl. schematic], July 1957, 32 pp.  (courtesy Heinz Blumberg, DC4GL)

As the type designator "T empf 40" suggests, this Hellschreiber is an "Empfänger", i.e., printer-only. It is for asynchronous operation ("quasi-synchronous") like the Feld Hell (though at twice the speed). Hence, the printer spindle has a 2-turn winding, and two parallel lines of text are printed onto the paper tape.  

The Siemens-Hell-Schreiber "F" - "T empf 40"

CHARACTERISTICS:

	Transmission rate: 5 or 5½ characters per second (selectable)
	Telegraphy speed: 245 Bd or 269½ Bd (5 vs 5½ cps)
	Modulation: On-Off-Keyed single-tone of 1000 Hz
	Size of printed characters: 2.5 x 4.5 mm (WxH).
	Paper tape width: 15 mm (like the Feld-Hell and Hell-80)
	Printer helix: 2-turn (like the Feld-Hell and Hell-80)
	Ink roller: same as Feld-Hell, 72 "GL", and Hell-80
	Motor: single-phase induction motor with electronic regulator (speed control knob under the lid of the unit, next to the roll of paper tape)
	Nominal motor speed: 1900 or 2100 rpm (5 vs 5½ cps)
	Input bandpass filter: center frequency 1000 Hz. Filter bandwidth is 700 Hz.
	Line impedance: 600 ohm (standard POTS telephone land-line) or 4000 ohm (radio)
	Minimum input signal: 10 mV into 600 ohm
	Paper tape speed: 1.05 or 1.15 m per minute (5 vs 5½ cps)
	Power: 220 Vac, 40-60 Hz, 45 VA
	Remote control: tone pulse of 1 sec (paper transport "on") or 6 sec ("off")
	Accessory: "Bandaufwickler" (winder for the printed tape), switched on/off via same remote control.

The T empf 44 is basically a T empf 39 receiver/printer, expanded with a character drum for a limited character set (0-9 and A-G). These units were used in telephone exchanges, for the purpose of recording fault codes. There is no keyboard or punch tape reader. Instead, there is a dedicated control input for each selectable character. Upon receipt of a fault signal, the associated character is printed locally. Compared to model 44c, model 44e has an additional contact, that allows the selected character to be transmitted to a T empf 39 in the local telephone exchange, or elsewhere. These models date back to the 1960s. The housing of model 44c has rounded corners and edges, whereas model 44e has right-angles .

CHARACTERISTICS:

	Characters set: 0-9 and A-G
	Transmission speed: 6.1 characters/sec - Model 44e only
	Telegraphy speed: 300 Baud - Model 44e only
	Audio frequency of sent pixel pulses: 1000/3000 Hz (selectable; to be confirmed) - Model 44e only
	Power: 60 Vdc (possibly also 48 Vdc (4x 12 V), to be confirmed. Telephone exchanges normally has a central 48 Vdc battery that is trickle-charged from the main Vac power. Different countries uses different DC voltages, but they are normally 36, 48, or 60 Vdc.)
	Dimensions: 31½x24x19½ cm (≈12x9½x7½")
	Weight: 9.3 kg (≈20.6 lbs)

The Siemens-Hell-Schreiber "T empf 44c" stacked on top of a T empf 44e"
(photo courtesy Heinz, DC4GL)

The Siemens-Hell-Schreiber "T empf 44c"

The inside of a Siemens-Hell-Schreiber "T empf 44c"
(photo courtesy Heinz, DC4GL)

The T send 62a (a.k.a. model "S") is a Hell character sender that is punch-tape driven ("Lochstreifensender"). So it has neither a keyboard, nor a printer. It has buttons for remote control of a compatible printer. It could also send a pause character (like the Feld-Hell). The unit is powered by a DC collector motor, with a centrifugal speed regulator (like the Feld-Hell machine).

 If you have any additional information or documentation on this model, please contact me!

(source: Bild 279, p. 362 in ref. 7)

CHARACTERISTICS:

	Punch tape coding: standard 5-bit CCIT alphabet nr. 2
	Transmit speed: 5 (5.5) characters/sec (selectable)
	Telegraphy speed: 245 (269.5) Baud
	Audio frequency of sent pixel pulses: 900, 1000, 1500 Hz (selectable)
	Output signal level (manually adjustable): -4 Neper - + 1.5 Neper (-34.7 - +13 dB) at 900 Hz -4 Neper - + 1.6 Neper (-34.7 - +13.9 dB) at 1000 Hz -4 Neper - + 1.8 Neper (-34.7 - +15.6 dB) at 1500 Hz
	Output impedance: 600 ohm
	Variation of audio output frequency: < 1 Hz for 10% AC voltage variation
	Power: 220 Vac, 40-60 Hz
	Dissipation: 50 VA
	Fuse: 200 mA (5x20 mm)
	Tubes (valves): 1x EF14 (pentode), 1x EZ11 ("Zweiweggleichrichter", "full wave rectifier"); both "Stahlröhre" ("metal-can tube") with 8-pin T-type base.
	Dimensions: 44x32x21 cm (≈17x12¾x8¼")
	Weight: 20 kg (≈44 lbs)

         
EF 14 tube

Apparently, in 1948 the Hell company used parts of other machines to manufacture a small number of two Hell Scheiber Empfänger models ("printer-only" Hellschreibers): HE 5 and HE 6. I.e., they did not have a Siemens-Halske model number "T empf".

 If you have any additional information or documentation on these models, please contact me!

In 1949, the Hell company developed a "Blattschreiber" based on the Hellschreiber principle. I.e., a page-printer instead of a tape printer. I don't know yet what its Siemens-Halske model name/number or type designator is. This model is not to be confused with Blattschreiber fax machines that Hell developed years later ("BS" models).

Hellfax-Blattschreiber BS109 and BS116 - these are not "Hellschreibers"
(source: figure 306 and 307 in ref. 7)

In order to print a line of text across a sheet (or roll) of paper, the printer head must be moved  across the sheet. Doing so with a Hellschreiber printer helix is rather cumbersome. But note that the helix-based Hell printer is in essence a column-printer that continuously sweeps across the paper tape. When the next sweep starts, the paper tape has moved over by one column width. When a tone pulse is received, the paper tape is tapped against the inked helix by a small solenoid-powered hammer, and a line segment is printed on the tape. The length of the line segment is proportional to the width of the received pulse.

A column printer can also be implemented differently, without a spindle, but still with a solenoid-powered hammer. Instead of a helix, there is a wheel with a relatively large diameter, see figure below. The blade of the hammer is installed tangentially to the circumference of the wheel. When the blade is tapped against the wheel, it only touches the wheel at a point. Ink is provided by an inked ribbon, as in a conventional typewriter. The paper is wrapped tightly against the wheel, and the inked ribbon moves between the hammer and the paper. If the wheel does not turn, then only a dot would be printed on the paper when the hammer blade taps the ribbon against the paper.

Conceptual dot-printer

Side-view of the conceptual dot-printer

To print a character, or a line of text, we still need to move the printer mechanism with respect to the paper, or vice versa. Let's expand (1) the paper tape to a paper sheet, (2) the printer wheel to a printer cylinder that is as long as the paper sheet is wide, and (3) the pinch roller across the full length of that cylinder. The cylinder is similar to the rubber-covered steel cylinder (a.k.a. "platen") of a standard typewriter.

All that we need to do now, is to move the hammer blade along the printer cylinder. Instead of moving the solenoid together with the hammer blade, we can use two stationary solenoids that are energized simultaneously. The solenoids actuate a hammer bar that is installed along the entire cylinder. The hammer blade moves at a constant speed across the printer cylinder, i.e., across the paper sheet that is wrapped around the printer cylinder. This is basically the same speed as that of the paper tape in a tape printer. The cylinder (and, hence, the paper sheet) also turn at a constant speed.

How can we use this concept to print letters, column by column? Very simple: you can not! As with all Hell-printers, the text characters consist of a matrix of columns and lines. The first and last column remains blank, to provide space between adjacent characters. Let's assume that we have a line of text. This is actually a large matrix that is a concatenation of a number of individual character matrices. One option is to transmit (scan) and print such an extended matrix in a column-by-column fashion. As stated above, this is not compatible with the Blattschreiber concept. Remains the option to print the entire top line of the extended matrix (i.e., spanning the entire line of text), then the one below it (of the same line of text), etc. This does require that the entire line of text must be known before its transmission can be started.

Column-by-column scan (left) vs. line-by-line scan (right)

If we only use a single hammer blade, then it would have to do a every fast "carriage return" to instantaneously fly back from the right-hand edge of the paper, back to the left-hand edge. Of course, this is not feasible. So we need at least two hammer blades: the second one is ready to go when the first one reaches the end of a text line. The easiest construction is attaching the blades  to a belt or a chain. The belt moves at a constant speed, and its track is such that the hammer blades move close, and parallel, to the printer cylinder. E.g., a track with the shape of a race track. See the diagram below. However, if we only use two hammer blades, then its is impossible to space them evenly along such a  belt: the distance between the blades must be equal to the width of the paper sheet, but the belt is longer than twice that distance. This problem is solved by using three blades that are spaced equidistantly. This is what has been done in the Blattschreiber. Of course, we could use, e.g., four  blades (ref. Hell patent  832444), but then the belt becomes unnecessarily long (the distance between blades is fixed), and more difficult to fit inside the printer. Note that the belt speed is independent of the number of blades.

Simplified mechanism of the sheet-printer

The next two diagrams provide a detailed illustration of how the above concept is actually implemented in the Hell-Blattschreiber.

Printer of the Siemens-Hell-Blattschreiber

(source: Figure 1, in Hell patent 832444)

Item 1 is the printer cylinder, called "Rippenwalze", as its surface has a number of longitudinal "ribs". The ribs do not appear to be essential to the printing process.

Printer of the Siemens-Hell-Blattschreiber

(source: Figure 291, p. 369 in ref. 7b)

As stated before, the printer cylinder turns at a constant speed while the hammer blade moves at a constant speed across the paper. If the path of the hammer blade were parallel to the axis of the cylinder, then the printed text line would have a downward slant, with a fixed angle. To counteract this, the printer mechanism is installed at an equal but opposite angle (upward slant).

Right hand view of the opened Siemens-Hell-Blattschreiber

(photo courtesy Jan Smeets, ex ON4ASZ/EA3DPB)

Left hand view of the opened Siemens-Hell-Blattschreiber

(photo courtesy Jan Smeets)

Bottom view of the opened Siemens-Hell-Blattschreiber

(photo courtesy Jan Smeets)

The printer is dimensioned to print lines of 69 characters. Without some form of synchronization between the text sender and the printer, the 69^th character of a line would typically be printed partially at the end of that line, and partially at the beginning of the next line. Contrary to some publications, the Blattschreiber does not use start-stop synchronization at character level. However, there is synchronization at text line level: "Zeilensynchronisierung". This requires that a special control unit ("Steuergerät") be connected to (or included in) the Hell Lochstreifensender (punch tape reader + sender). The Lochstreifensender chops the text that must be transmitted, into strings of 69 characters. It also adds a special line-sync character at the beginning of each line-string, and ensures a fixed string length of 69 characters by using blank characters at the end of the string (if necessary). The synchronization is based on measuring the time difference between receipt of a line-sync character, and the momentary position of the hammer blade. This phase difference is used to slightly adjusting the local motor speed (up to +/- 1.4%), until the time difference is eliminated. The printer has a clutch mechanism for the blade movement.  Upon receipt of the stop-character, movement continues until one of the blades is exactly at the start position of a line. The printer has a clutch mechanism to halt chain with the hammer blades when one of the blades is exactly at the start position of a line. This is combined with remote control.

This mechanism only works for operation with a special "Lochstreifensender"  that chops up text into strings of 69 characters.  A special control unit ("Steuergerät") has to be connected to (or included in) the Lochstreifensender, to accurately control the start of text and text lines of the latter. 

The Blattschreiber is designed for 5 characters per second (cps), i.e., a telegraphy speed of 50 WPM. This implies almost 14 sec for a full line of text. Assuming a Hell font with 7 columns per character, there are 69 x 7 = 483 pixels per printed matrix line. Further assuming 7 lines per character, there are 483 x 7 =  3381 pixels per line of printed text. That is, 14000 / 3381 = 4.14 msec per pixel.

According to ref. 7, the Blattscheiber has a mechanism to repeat the 69^th character at the beginning of the next line. Note that this trick is also done by all software-implemented Hellschreibers that came several decades after the Blattschreiber! The same effect can be obtained by simply reducing the length of the belt, such that the space between the hammer blades is reduced by the width of one character (ref. lines 23-30 in Hell patent 848970).

If you have any additional information or documentation on this model, please contact me!

	Ref. 7: "Die Schreibenden Drucktelegraphen" [47 MB], Fritz Schiweck, section 9.5 (pp. 358-378) of "Fernschreibtechnik",  Band 9 of “Lehrbücher der Feinwerktechnik“, 4th ed., 1962, C. F. Winter, 894 pp. Ref. 7a:  Section 9.5.2.2 (pp. 360-363) Ref. 7b: "Siemens-Hell-Blattschreiber", Section 9.5.2.6 (pp. 368-372) .
	Ref. 8: "Der Blattschreiber für das Siemens-Hell Verfahren", R. Zimmermann, Entwicklungsberichte der  Siemens & Halske Aktiengesellschaft, Jg. 15, 25 May 1952, pp. 9-12 (also appeared in VDE-Fachberichte, Vol. 15, 1951)

Below is a listing of Hell patents related to the Blattschreiber. Some of the patents describe printer-head mechanisms other than the one described above.

Patent office abbreviations:

BD = Bundesrepublik Deutschland, Deutsches Patentamt

CH = Swiss Patent Office (Schweizerische Eidgenossenschaft - Eidgenossisches Amt für geistiges Eigentum)

Patent source:

DEPATISnet, the on-line public database of the Deutsches Patent- und Markenamt (DPMA, German Patent and Trademark Office)

 If you have any additional information or documentation on this model, please contact me!

The Luftwaffe also used Hellschreiber technology for aerial navigation, as part of the "Berhard" system. The ground-station transmitted the momentary azimuth of its narrow-beam antenna in Hell format on VHF (30-33.3 MHz), as the antenna rotated (ref. 3). Its airborne counterpart is a small Hell-printer, the FuG 120 "Bernhardine" ("UKW-Richtstrahl-Drehfunkfeuer Empfänger" or "Receiver for VHF rotational directional beam beacon"; Actually two simultaneous printers: "bar graph" signal strength (to identify the "null" of the transmitter antenna pattern) and Hell (bearing etc).

Airborne counterpart of FuSAn ("Funk Such Anlage") 724/725 "Bernhard" UKW-Richtstrahl-Drehfunkfeuer [ built by Telefunken]

FuG 120 »Bernhardine«: Hersteller Siemens.

FuG 120, 120s, 120b, 120k

FuG 139 "Barbarossa"

FuG Funkgerät

Measured 60x30x20 cm.

It was installed in various aircraft types, esp. night fighter versions, such as: the Messerschmitt Me262A (one of my all time favorite aircraft), Junkers Ju 88G, Arado Ar234 (ref. 4), Dornier Do-335 "Pfeil".

Mid-1944

Intended to replaced the "Knickebein" system.

Berhardine FuG 120a bearing displayed on paper tape by a Hell printer
(Figure 14 in ref. 12; also: Figure on p. 99 of ref. 17)

Berhardine Registrierungschrieb (printout)
(Figure on page 97 in ref. 16)

Sample message. The night fighter is on bearing 090 from the station, the point of the Bomber Stream is at an altitude of 4.000 m, at map grid KP [A?], on heading 270, estimated strength 100 aircraft.

L Peilschreiber (bearing printer)"Psch 120" of the FuG 120a; R: "Psch 120a" of FuG 120 b
(Figure on page 11 in ref. 15)

FuSAn ("Funk Sende Anlage") 724/725 "Bernhard" UKW-Richtstrahl-Drehfunkfeuer [built by Telefunken]. The system consisted of a very large antenna (please see below) which rotated 360 dg. twice a minute. The receiver in the aircraft (FuG 120 "Bernhardine") displayed the bearing to the station on a narrow paper strip. The system was modified to transmit a very abbreviated "Reportage Lage" consisting of the height of the Bomber Stream, the position, heading and strength. The system worked on 30 - 33,3 MHz, was high powered, directional and hence very difficult to jam. By switching between 2 stations the radio operator could obtain a fix every 1 minute and he did not have to work 2 radios to find a jamming free frequency.
 

Funkmessgerät.

Die Anlage drehte sich zweimal pro Minute auf einem Schienenkranz. Dabei wurde die Stellung der Sendeantenne als Modulation ausgesendet. Außer einem sogenannten Hellschreiber (FuG 120 Bernhardine) wurde keine zusätzliche Funkausrüstung benötigt, da entsprechende UKW-Empfänger (30 bis 33 MHz [Fu Bl 1 (cf. ref. 7 for the manual) (Funk-Landegerät) dieses zwischen 30 und 33,3 MHz arbeitende Gerät war ein Empfänger für den UKW-Landeleitstrahl, or FU Bl 2 (expanded freq range); TBC if used with FuG 125 "Hermine"; Range 200 km??; FuG139?) schon Bestandteil der Bordausrüstung waren. Der Hellschreiber zeichnete die empfangenen Signale auf einem Papierstreifen auf.

Fu Bl I Fu Bl 1

CHARACTERISTICS:

	Frequency: 30 bis 33 MHz
	Transmitter power: 2 × 500 W (5000 W ERP)
	Range: 400 km (at flight altitude of 5000 m / 16000 ft)
	Accuracy: +/- 0.5°
	Manufacturing: starting in 1941
	Transmitter antenna dimensions: 28 x 35 m (HxW, 92x115 ft)
	Antenna system track diameter: 22.6 m (74 ft)
	Antenna system weight: 120 t (265000 lbs)

The "Bernhard " station at Hundborg/Thisted (northwest coast of Denmark)
 

	Ref. 10: "Bernhard and Bernhardine", p. 24 in "Some historical and technical aspects of radio navigation, in Germany, over the period 1907 to 1945", by A.O. Bauer, PAØAOB, December 2004, 28 pp.
	Ref. 11: p. 18 in "Blitz!: Germany's Arado Ar 234 Jet Bomber", by J.R. Smith, E.J. Creek, Merriam Press, 1997.
	Ref. 12: "Empfangsseitige Schreibvorrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung" Patent 767536A, Adalbert Lohmann, March 1936, published 1952 (!); addendum to patent 767345.
	Ref. 13: p. 350 in "Geschichte der deutschen Nachtjagd: 1917-1945", Gebhard Aders, 1977, 391 pp., Motorbuch Verlag, ISBN-10: 387943509X. Also appeared as translation with revisions: "History of the German night fighter force, 1917-1945", Jane's Information Group, 1979, ISBN 0867205814, 360 pp.
	Ref. 14: pp. 84-87 in "Die deutschen Funkführungsverfahren bis 1945", by Fritz Trenkle, Alfred Hüthig Verlag, 1987, ISBN 3778516477
	Ref. 15: pp. 96-102 in “Die deutschen Funk-, Navigations-, und Funk-Funkführungsverfahren bis 1945“, Fritz Trenkle, Motor Buch Verlag, ISBN 3879436150,1st ed., 1979, 208 pp.
	Ref. 16: "Beschreibung und Betriebsvorschrift für Funklande-Empfangsanlage Fu Bl 1 Ex", DTA 140, C. Lorenz AG, 1940, 61 pp.

Around 1960, Hell developed optical-scan paper tape fax. These machines were used by Air Traffic controllers (to exchange flight info strips), weather services at airports, police (to transmit fingerprint cards, restaurants, factories, labs, etc. It is called ZETFAX, short for "Zettelfax" ("Zettel" = note, slip of paper)

ZETFAX "Geber" (sender) and "Schreiber" (printer)
(note the classical printer mechanism in the receiver on the right)

At the sender side, text is handwritten onto paper tape. The paper tape is pulled through an optical column-scanner. Light from a small light bulb is passed through a special lens that casts a bar of light across the tape. The light bar that is reflected off the paper, is passed via simple optics through a narrow slit and a spinning Nipkow-disk (a series of small holes, arranged on a 1-turn spiral; conceived by Paul Julius Gottlieb Nipkow (1860-1949) on Christmas Eve of 1883). Each revolution of the disk represents one column-scan across the paper. The holes in the disk effectively "chop" the column-scan into light pulses. These pulses are captured with an optical sensor. The analog brightness signal from the sensor is passed through a level-detector (threshold) to digitize it. The resulting binary DC-pulses are converted to tone-pulses and sent to the printer at the opposite station. As with other Hellschreibers, transmission can be done via phone lines and radio. The printer is basically a classical Feld-Hell spindle-printer. It has a spindle with a 1-turn thread. It uses the same type of paper tape as the the sender. The Nipkow-disk also creates a start-pulse, to synchronize the sender and the receiver/printer. On the printer side, this (dis-)engages a clutch on the printer spindle.
 

Characteristics:

	Paper-scan and transmission speed: 19 cm/min (7½"/min) @ 50 Hz, 23 cm/min (9"/min) @ 60 Hz
	Image resolution: 4 lines / mm
	Scanner input: HT206 (paper-tape scanner/sender): 38 mm (1½") wide paper tape HT 236 (paper-piece scanner sender): paper pieces, 38 mm wide and 66, 102, or 152 mm long. scanned width: 25.4 mm (1")
	Printer output: 38 mm (1½") wide paper tape printed width: 25.4 mm (1")
	Tone frequency: 1500 Hz +/- 700 Hz
	Equipment size (HxWxD) and weight: HT206 (tape scanner):   14x36x34 cm (≈ 5½x14x13"), 14 kg (≈ 31lbs) HT236 (piece scanner): 18x36½x37 cm (≈ 7x14x15"), 16 kg (≈ 35lbs) HT207 (tape printer):      15x22x31 cm (≈ 6x9x12"), 9 kg (≈ 20 lbs)

References:

	Ref. 17: "Nog een hell-systeem", A. van Ooijen, PE1AQB, Electron, 8/1983, p. 417 [optical Hell, ZETFAX]
	Ref. 18: "ZETFAX, aus der Praxis, für die Praxis" [Hell Co. optical-scan + Hellschreiber tape printer], Rudolf Hell GmbH, 1968, 19 pp., ZA-2-6807(592).
	Ref. 19: "Interavia: world review of aviation-astronautics-avionics", vol. 22, nr. 6, 1967, p. 913

Listed below are Hell patents related to the optical scanning and transmission of text printed on paper tape.

ZETFAX-Geber Typ HT 236 (left) and ZETFAX-Schreiber Typ HT207 (right)
 

Examples of handwritten ZETFAX strips (blank paper and and preprinted forms)
(aerodrome meteo report, 2x lab analysis results, hotel breakfast order; source: ZETFAX advertising brochure)
 

Source: ref. 19

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