TMC produced this compact telephone for Telephone Rentals and probably other suppliers. This telephones has two capacitors (in the same casing) an induction coil and bell on the base plate. 

In the body of the phone is an 8 way style terminal array with only 6 terminal connections and unlike Ericsson and GEC compacts, is the only terminal block within the phone.  The terminal block has screws instead of nuts.  Sometimes there is an insert fitted in terminal 7 but is will have no screw and no wiring connected to it.

The base plate accommodates the capacitor, the bell ringer, bell gongs (barrel shaped) and induction coil.  The base plate also has oblong slots covered with mesh, which stop insects and foreign objects entering the telephone.

The case is straight edged at the bottom, has a full size base plate and two cable entry holes on the rear, which have ebonite grommets.

Very similar to the S52596 except the S52597 terminal block has only 6 connections.

The cylindrical capacitor, which is the GPO Capacitor M.C. 97, was introduced circa 1947, whilst PVC insulated wire was first used in telphones in the late 1940's.

Click here for more information on compact telephones.



Diagram S52597

How to convert this telephone to the UK PST System

Using a standard UK line cord:-

  1. Remove and discard the old line cord.

  2. Feed the new line cord through the casing entry hole and tie it or knot it to the metal loop inside the phone.

  3. White wire of new line cord to terminal 4.

  4. Install a 3.3k resistor between 4 & 5.

  5. Red wire of new line cord to terminal 6.

  6. Green wire of new line cord - spare - insulate.

  7. Disconnect the green wire on 2uf capacitor and connect this to the Blue wire of the new line cord (insulate with tape).

  8. Check transmission and replace transmitter if bad and always fit a Rectifier element across the receiver on terminals 1 & 2.  Click here for more information.

Additional Pictures

Rear view - note the twin cable entry holes with ebonite grommets


View of the base plate - 5 oblong sound exit slots covered with mesh


Internal view of the case - No components are mounted within the case


Internal view of the base plate showing components


Capacitor markings - In this case there is no date
S113550 is the TMC code for this capacitor


The "TR" symbol is found on the handsets of phones produced for Telephone Rentals



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Last revised: January 07, 2023