GEC AUTOMATIC TELEPHONE
Catalogue Nos. ST3500 series (Standard) and ST3600 series (Tropical)
A table telephone of modern design, for use with all automatic switching
The corresponding telephone for C.B. manual systems is described in
The moulded Bakelite case, identical in shape with the latest British Post
Office model, combines a robust design with a pleasing simplicity of line.
All components except
the dial are mounted on a main assembly plate, which can be withdrawn from the
case very easily as a complete unit.
The G.E.C. dial is the British Post Office standard, with a stainless steel
finger-plate which retains its high
The cradle-switch mechanism has been specially designed to eliminate any
likelihood of sticking plungers. Twin contacts give maximum reliability.
The handset is the well-known moulded Bakelite Gecophone pattern, with inset
type transmitter and receiver.
The flexible handset cord will give exceedingly long service; the conductors
are made from tinsel that withstands 200,000 reciprocations without
strip, connecting the
incoming line wires
to the telephone cord, has moulded separators between terminal plates to
maintain long leakage paths.
There are separate entrances for the line wires and
The transmitter and receiver are British Post Office standards, and the
high-efficiency speech circuit gives maximum volume with uniform frequency
response and excellent sidetone suppression.
The unfailing efficiency of the G.E.C. dial mechanism is well known and a
special spark-quenching circuit protects the dial impulsing contacts during
If required, a suppression circuit can be included to prevent interference with
nearby radio receivers during dialling.
G.E.C. telephones for service in tropical climates incorporate various
special features, which are the result of long experience (see picture above):-
- A shunt is connected across the transmitter to minimise the minute arcing that
tends to occur at the granules and electrodes as: the cradle switch operates;
the accelerated tendency towards frying often shown by transmitters in the
tropics is thereby offset. The effect of any increase in transmitter resistance
upon line circuit conditions is also minimised by the shunt. The loss in volume
efficiency is very small and is partly cancelled by reduction of sidetone, the nett result being a difference of only 1 db. Should the conditions of use render
the protection unnecessary and require the very maximum of volume efficiency,
then the shunt may be disconnected by the simple transfer of one wire from one
terminal to another.
- Ventilation holes in top and bottom of the case allow air to circulate freely
through the case to minimise condensation.
- All apertures are covered with fine wire gauze to prevent the ingress of
- Metal parts are specially finished, and all wiring is specially treated, to
resist the effects of high humidity and salt-laden atmospheres.
- Cradle-switch springs have large insulators to
ensure long leakage paths.
- Flexible cord conductors are V.I.R. covered and braided overall. Since textile
bindings at the ends are not in contact with the conductor, moisture absorption
cannot cause leakage. Rubber fittings give mechanical protection at points of
entry to the mouldings.
- All coils are specially treated to render them impervious to damp, heat and
sudden changes in temperature.
- For very dusty atmospheres, a bakelite cover can be fitted to the back of the
dial to give complete enclosure to the mechanism.
Earlier model shown - identified by the flat switch hook
The standard colour is Black but enquiries are invited for the telephone in
Ivory, Jade Green or Chinese Red, with cords finished to match.
A magneto extension bell in the G.E.C. Cat. No. BE1100 series (Standard) or
BE1200 series (Tropical) is recommended for use with this telephone, to provide
calling signals at a distant point, indoors or out, or to augment calling
signals in very noisy surroundings.
Length - 7.25" (18.4 cm)
Width - 9" (22.9 cm)
Height - 6" (15.2cm )
Weight - 5.5 lbs. (2.5 kgs)
Enquiries and Orders
Please state on all enquiries and orders:
- Finish - whether standard or tropical
- Colour required.
- If batteries are to be supplied and whether they are to be active or
- For component parts, please refer to item by name and quote catalogue
number of complete instrument ; for example, "Handset cord for Telephone
Cat. No. ST3101".
Taken from the GEC Catalogue Leaflet No. STL.3
(1955 PART NUMBERS SHOWN IN BRACKETS)
|ST 3301 (TEL/1P/CTS)
||ST 3403 (TEL/2P/CTT)
||332 C.B. Manual
|ST 3504 (TEL/1P/ATS)
||332 Automatic Non-Director areas
|ST 3505 (TEL/1P/ATS/1)
||332 Automatic Director areas
||Automatic Director areas - minor variations
||Automatic Director areas - minor variations
||ST 3608 (TEL/2P/ATT)
||Automatic Dial Non-Director areas
|ST 3521 (TEL/9P/ATS)
||ST 3621 (TEL/10P/ATT)
||Automatic for D.C. ringing.*
|ST 3551 (TEL/3P/ATS)
||ST 3651 (TEL/4P/ATT)
||312 Automatic two-party line, selective ringing, non-director
|ST 3552 (TEL/3P/ATS/1)
||ST 3652 (TEL/4P/ATT/1)
||312 Automatic, two-party line, selective ringing, director
Note : * For use with the 10-line All Relay P.A.X. Cat. No.
PX1110 (Standard) and
Circuit Diagram for the ST3608 - KS9645
To Convert the ST3608 to work on the UK plug
and socket system
Remove existing line cord.
Connect the red wire of the new line cord to L2.
Replace the link between E and L1 with a 3.3k resistor.
Insulate the green wire of the new line cord.
Connect the white wire of the new line cord to L1.
Disconnect the black wire from the 2uf capacitor.
Connect the blue wire of the new line cord to the black wire
Connect a Rectifier No. 205 between R and MR.
ST3505 Black - standard automatic telephone with Director
dial (letters and numbers)
ST3604 with chassis removed. This is a later model
with the "non-stick" switch hook plungers
Pictures below are all ST3608 models
Manufacturers marking on handset
Close up of interior of Terminal Block
Circuit diagram pasted to base plate
Baseplate showing model number.
Interior view of telephone