Siemens-Hell-Schreiber model 44 was developed during the 1960s. But, unlike all other Hellschreibers, not for general telecommunications, but in telephone exchanges: as part of automated test equipment such as the Automatische Prüfeinrichtung APrE 50 and the Routineprüfeinrichung (RPE). Four versions of the "44" were developed:
- 44 C: it prints out the identification of occupied exchange switches, and failed switches.
- 44 E: same as 44 C, but simultaneously prints the status messages at a remote T.empf.39 printer at the next upper-level telephone exchange. Therefore, and unlike model 44 C and F that are printer-only, model 44 C is a printer/sender and operates with the start-stop system.
- 44 F: prints status data from Prüf- und Alarmregistriereinrichtung system (PAR; test & alarm-recording) of private branch exchanges (PBX), such as the Siemens ESK-3000E.
Note that unlike all other Siemens-Hell models, its only model designator appears to be simply "44", not T.empf.44, T.typ.44, or T.send.44. Possibly, because it is neither a printer-only model ( = T.empf), nor does it have a keyboard ( = T.typ), nor is it a sender-only ( = T.send).
Figure 1: model 44C (left), 44E (item K = speed adjustment knob), and 44F (item LT "Lauftaste" = paper advance button)
(source: Fig. 1, 2, 3 in ref. 1)
Through the mid/late-1960s, the housings did not have straight comers as in the photos above, but rounded corners, as in the photo below.
Figure 2: An early model 44F (with rounded corners)
The main characteristics of model 44 are (ref. 1):
- Transmission rate:
- Model 44 C & F: 5.5 -7 characters/sec (6.1 char/sec nominal)
- Model 44 E: 6.1 char/sec
- Standard 7x14 Hell-font
- Model 44 E sends the 7x14 Hell-font with start pulse.
- Character drum: a stack of 19 or 20 notched disks with associated slip-contacts
- 7 letters (A-G)
- 10 figures (0-9)
- 1 punctuation mark ("-" dash)
- 1 pulse for incrementing a telephone exchange rotary-switch ("Synchronnockenscheibe")
- Model 44 C and E have an internal exchange switch, connected to the pins of blade-connector St2 ("Stecker 2") on the rear of the unit.
- Model 44 F sends the pulses to a chain of external exchange switches ("Zählerkette"). It does not have an St2 connector.
- 1 start-pulse (model 44 E only)
- In model 44 C and E, the character pixel-pulses are sent to the test equipment via St1 ("Stecker 1") on the rear of the unit. they are wrapped-back via the test equipment, and then go to the printer module.
- In model 44 F, the pixel-pulses go directly to the unit's printer module.
- Remote control: only model 44 E is connected to a remote T.empf.39 printer. In case of an alarm or detected fault, the test equipment "wakes up" the T.empf.39, waits for the "ready" ("Bereit") back from the T.empf.39, then activates the 44 E.
- Paper tape width: 9.5 mm (like the T.empf.39, T.typ.72 and T.typ.73)
- Printer helix: single-thread, 2-turn
- Motor: shunt-wound ("Nebenschluß") DC motor, 2600 rpm nominal
- Model 44 C and F: no speed regulator; speed adjustment simply with a variable series-resistor (potentiometer).
- Model 44 E. centrifugal speed regulator, with speed adjustment knob under the lid of the unit, next to the roll of paper tape. The 44 E needs to maintain the nominal speed better than ±2%, as it also transmits to a remote T.empf.39 start-stop printer.
- Power: all models were available in versions for 48 and for 60 volt DC operation. I.e., the world-wide standard operating voltages of telephone exchanges and systems. Power consumption: ca.35 watt.
- Size: 32x26x20 cm (WxDxH, ca. 12.6x10.2x8 inch) - same as the T.empf.39 and T.empf.40.
- Weight: 10 kg (≈22 lbs)
Fig. 3: The inside of a model 44E - note the stack of 19 notched disks and motor with centrifugal regulator
(source: Heinz Blumberg; used with permission)
Figure 4: Typical diagnostic print-out of a model 44
(source: Fig. 4 in ref. 1)
Figure 5: Front of model "44 E"
(original unedited photo: eBay 2016)
Figure 6: Rear of model "44 E"
(original unedited photo: eBay 2016)
Figure 7: A model 44C installed in an APre50 test rack (left) and a 44C stacked on top of a 44E
(source left: J. Hartl, Museum für Kommunikation/Frankfurt; right: H. Blumberg, used with permission)
Fig. 8: A 44 in an RPE test rack of the exchange in Wien-Fünfhaus/Austria (left) and a 44C in a German international exchange
(source left: private collection of N. Dulosy in Laa a/d Thaya/Austria; right: ref. 2)
- Ref. 1: "Siemens-Hell-Schreiber 44 - Beschreibung", Siemens AG, Bereich Fernschreib- und Datenverkehr, A22232-A44-A3-1-18, Ag 02730.2, December 1972, 23 pp.
- Ref. 2: "New International Telephone Switching Center in Düsseldorf" in "NTZ-Communications Journal" (NTZ-CJ), No. 3, 1967, p. 146, 147 [T empf 44c]
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