Modified 300 type table telephone, used with Privacy Sets No. 6 and No. 7 on Automatic and C.B. systems.  The Privacy sets were speech scramblers and afforded secure communication to a distant privacy set.  Privacy sets are also known as Frequency Changers.

These telephones were generally built up, when required, using a Telephone No. 328 Black and a Telephone No. 164 Green.  The green handset was a to allow easy identification of the secure phone.

The telephone had provision for three press button keys.  Normally the middle button would be left blank and only used if recall facilities or a ring button were required.  The left button was originally labelled "Secret", which later changed to "Scramble" and the right button labelled "Normal".

The newly introduced Receiver Inset No. 2P was also specified for these telephones as the reception quality was considerably better than the Receiver Inset No 1L.  The Receiver Inset No. 2P also used the newly introduced Earpiece No. 23 and due to war time shortages black earpieces were used when green was not available.  When green handsets were not available the GPO Factory would paint the handsets a Lime Green colour.

Factory modified sets would have been marked SA 5030 but those built in the field would have retained the original Telephone No. 328 markings on the base and chassis.

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Introduced in 1940.

Circuit diagram - SA 5030.

Installation Instructions

Telephone SA 5030 comprises of the following:-
1 x Telephone No.328 C.B. Black minus cord and handset
1 x Telephone No.164 Green fitted with a Receiver, Inset No. 2P and an Earpiece No. 23 Green.
2 x PARTS No. 1/SPL/325
1 x Key No. 303A
1 x Label No. 252R
2 x Cords, Instrument No. 6/ 21B Brown 54"
1 x Block Terminal No. 20/8 Black.

These are assembled and connected as follows:-

  1. Key No. 303A is fitted with control plate in position 3.  Plungers A & C are fitted and the extension arm is fitted to give gravity switch hook release (see N4301).
  2. Cord, Instrument No. 3/63A is disconnected form telephone terminals 4, 5 & 6 and reconnected as follows:-
    White to terminal 19 of Key No. 303A.
    Red to terminal 24 of Key No. 303A.
    Green to terminal 27 of Key No. 303A.
  3. The following are connected together.
    Telephone terminal 4 to Key No. 303A terminal 20.
    Telephone terminal 5 to Key No. 303A terminal 23.
    Telephone terminal 6 to Key No. 303A terminal 26.
    Telephone terminal 9 to Key No. 303A terminal 17.
  4. Telephone terminals 1 & 2 are strapped together.
  5. Telephone terminal 1 and Key Terminals 16 & 18, 21, 22 & 25 are connected by Cord, Instrument No. 6/21B Brown 54" to the Block Terminal.

Privacy Set No. 6A internal view

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Last revised: February 21, 2023