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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), and the Presse-Hell. Hence, the printer spindle has a 2-turn thread. It prints two identical parallel lines of text onto 15 mm wide paper tape. The T.empf.40 is also knows as model "F".

T empf 40

Data plate of two model "F" Siemens-Hell-Schreibers

(1945 was Siemens year "A"; the serial-number on the left label is from 1955 (year "K"), the one on the right from 1956)

Model "F" is the replacement of the ubiquitous "Presse Hell" (T empf 14; 7x14 pixel font). Actually, there are two versions of the T empf 40:

  • 40a: with a built-in tone detector and keying amplifier. It can simply be connected to the loudspeaker output of any radio receiver, whereas the Tempf 14 required an external amplifier/detector unit, or a special Hell-receiver with a built-in detector/driver. The two-stage amplifier of the 40a uses an EF80 and an EL83 vacuum tube (both are pentodes).
  • 40b: without a built-in amplifier. However, it has selectable AC-voltage power (version "a" is 220 volt AC only).

This model was used in combination with Siemens-Hell-Geber "S" (T Send 62a) and Siemens-Hell-Sendeanlage "Z" (ref. 1, 2). The South African embassy in The Netherlands is known to have used model "F", as did the monitoring station of Radio Free Europe at Schleißheim near Munich (ca. 1957, ref. 3).



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MODEL T.EMPF.40  "F"

T empf 40

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

(source: ref. 1)

The machine looks similar to models T.empf.39d "L" and 44c/e, but the "F" is the only model with a toggle switch in the lower right-hand area on the front. The main characteristics of the T empf 40a are:

  • Transmission rate: 5 or 5½ characters per second (selectable)
  • Telegraphy speed: 245 Bd or 269.5 Bd (5 vs 5½ cps)
  • Tone-detector/printer amplifier:
  • Modulation (model 40a only): On-Off-Keyed single-tone of 1000 Hz
  • 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 level: 10 mV into 600 ohm
  • Size of printed characters: 2.5 x 4.5 mm (WxH).
  • Paper tape width: 15 mm (like the Feld-Hell, Presse-Hell, and Hell-80)
  • Printer helix: 2-turn (like the Feld-Hell)
  • Motor: single-phase induction motor with electronic regulator; the speed control knob is located under the lid of the unit, next to the roll of paper tape.
  • Nominal motor speed: 1900 or 2100 rpm (5 vs. 5½ cps; selectable)
  • Paper tape speed: 1.05 or 1.15 m per minute (5 vs. 5½ cps)
  • Power (model 40a): 220 volt AC, 40-60 Hz, 45 VA
  • Remote control: tone pulse of appr. 1 sec (motor "on"), 6 sec ("off"); same as in the Presse-Hell printers.
  • Accessory: "Bandaufwickler" (winder for the printed tape), switched on/off via the remote control.
  • Size: 32x26x20 cm (WxDxH)
  • Weight: 12.6 kg (≈28 lbs)
T empf 40

Modular design of the "T.empf.40a"

(source: ref. 1)

Like the feld-hell and Presse-hell printers, the T.empf.40 has a spindle that prints two identical lines, one above the other. However, whereas the Feld-Hell and Presse-Hell printer modules have a 2-start spindle (two 1-turn threads, offset by 180°), the T.empf.40 has a 1-start 2-turn spindle, see the photos below. This is much easier to manufacture, but requires twice the rpm.

T empf 40

The printer-module and close-up of the 2-turn spindle

(source: R. Lampe; used with permission)


T empf 40

Print-out of a "T.empf.40a" (printed characters are 4.5 mm high)

(source: Fig. 21 in ref. 3)

T empf 40

Print-out of a "T.empf.40a"

(source: R. Lampe; used with permission)


T empf 40

A "T.empf.40" at the monitoring station of Radio Free Europe at Schleißheim near Munich (ca. 1957)

(source: ref. 3)


REFERENCES


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