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Telephone No. 740 was an analogue tabletop
telephone set with pulse-dialling,
suitable for use on automatically switched networks, introduced in 1968 by the
British General Post Office (GPO)
as the successor to Telephone No. 710 [1].
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Telephone No. 740 was one of the models that could be converted for
operation in combination with Privacy Set No. 8 — a telephone voice
scrambler that has its origins in World War II.
For this purpose, the 740 was modified with a 4K switch pack and
had two or more push-buttons at the top. Pressing the button marked
SEC'T transferred the call to the scrambler unit.
➤ More information
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- N840, Telephone No. 740 circuit diagram
GPO, 18 February 1969 - 12 Actober 1972. Issue A (1 page). 1
- N4700, Auxiliary Units and Additional Parts for 700-type Telephones
GPO, 12 August 1963 - 15 May 1977. Issue C (4 pages). 1
- N848, Auxiliary units for Telephones, Nos. 710, 711, 740, 741 & 746
GPO, 21 January 1969 - 9 May 1977. Issue J (4 pages). 1
- Press-Buttons for Tel. No. 710, 711, 740, 741 & 746
GPO, 10 February 1969 - 28 July 1980. (2 pages). 1
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Document obtained via [1].
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© Crypto Museum. Created: Monday 09 August 2021. Last changed: Tuesday, 10 August 2021 - 09:23 CET.
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