Creed Model 7 Page Teleprinter
The Creed model 7 page teleprinter, whilst not the first teleprinter to be produced by Creed it is, without doubt, the most well known of their machines, and is considered by many to be the teleprinter that helped the Allies to win World War 2. Many thousands of model 7’s saw service with the Armed Forces, sending vital messages around the world, and sending top secret messages to and from the code breaking teams at Bletchley Park in Buckinghamshire.
When the model 7 was finally introduced in 1931, it was a truly state-of-the-art machine.
1. Printing was done on paper 8½” wide, which was supplied in rolls 3½” diameter, with the rolls being carried on the carriage within the machine.
2. The typing was done through an ink ribbon, as on a typewriter, instead of the ink rollers running on the typehead as used on the model 3.
3. Ball bearings were used on all high speed shafts, and oil cups were provided on all small bearings so that the machine was capable of at least 100 hours continuous operation without attention.
4. Communication could be effected with a machine in an office without a receiving operator being in attendance. This feature, known as the “Absent subscriber service”, makes it necessary to provide a means which will enable the calling subscriber to verify that the correct connection has been made. For this purpose an “Answer Back” device was provided on the machine, which is arranged to send the exchange number of the called machine back to the calling subscriber whenever the calling subscriber depresses a particular key on the keyboard.
5. A signalling device was provided which could be used for calling the attention of the person in another office to any urgent message received. It could be caused to ring a bell or light a lamp.
6. In order to simplify the manufacture and maintenance of the machine, it was built in units. The model 3 was arranged that portions could be readily removed, but it was not designed so that it would be possible to remove a portion and replace it by a spare without re-adjustment being necessary. The model 7 was designed so that this was possible, leading to reduced maintenance costs, and making it possible to effect field replacements in the shortest possible time.
7. The automatic motor starting and stopping device was completely re-designed and provided with new facilities.
8. The general design of the machine was such that it could readily be adapted for any purpose within the range of start-stop telegraphy. This feature arises due to the keyboard unit and paper carriage being detachable from the receiving portion of the machine.
Two types of paper carriage were provided, one suitable for printing on a tape, just like the model 3, and the other on a roll of paper. During its production life of 38 years, over 101,000 model 7’s were produced, in many different versions. The original version, the 7A, transmitted a 7½ unit character, (i.e., 1 Start unit, 5 Code units, and 1½ Stop units) and had a 7 unit receive cycle. However, a CCIT (Comite Consultatif Internationale Telegraphique) recommendation was that machines should be capable of correctly receiving and printing characters when each character is sent out as 7 equal units. That is, with a stop signal of only one unit, instead of the usual 1½ units. A re-design of the receive camshaft and its drive mechanism reduced the receive cycle to 6½ units, and with the original 7½ unit transmit cycle this machine became the famous model 7B. There was also a version with a 7 unit transmit cycle, still with the 6½ unit receive cycle, known as the model 7C. This machine tended to be used only on private wire networks where the shorter stop element produced a slightly higher throughput of information. This was equivalent to 71 words per minute for the model 7C at 50 Bauds, compared with 66 words per minute for the model 7B at 50 Bauds.
The above details have been taken with thanks from the VMARS Newsletter Issue 31, 11 October 2003 from an article by Alan G Hobbs
The whole article can be seen at http://www.vmarsmanuals.co.uk/newsletter_articles/creed7b.pdf
Our model was very kindly donated by Robert Mirfin
This exhibit has a reference ID of CH6198. Please quote this reference ID in any communication with the Centre for Computing History.