A.T.M. Co's wall set used on the Strowger Automatic System.  Fitted with an Electro-magnetic receiver.

It is the phone used by the GPO on the two auto exchanges introduced in 1912 (Epsom, Surrey and the Official Switch [i.e. Post Office Headquarters] in London).

Also known as the Epsom type.

Very basic circuit, with dial, Receiver Bell No. 4 and transmitter all in series with no induction coil.

Telephone included (1928):-
1 x Dial Automatic No. 1 or No. 8FA.
1 x Bell No. 1A with bias spring.
1 x Condenser MC No. 3 or No. 30.
1 x Receiver Bell No. 4A.
1 x Switch Receiver No. 1.
1 x Hook, Receiver F.
1 x Transmitter No. 1.

The Receiver Bell No. 4A has no permanent magnet.  The American variant has a Diaphragm No. 9 and an Earpiece No. 4, whilst the Mark 234 has a Diaphragm No. 12 and an Earpiece No. 2.

Sometimes fitted to a Desk No. 4.

Telephones No's 55 and 55B were superseded by Telephone No. 105 or Telephone No. 121.

Circuit diagram - N155
Original diagram - A.T. 8.

Paster Diagram


Here is a picture of the insides of a Telephone No. 55.  All the brassware should be black and note the non-ATE dial, especially the way it is fixed!

Wiring for use in the UK

You are warned that this telephone has a very basic transmission circuit which is nothing like the quality of a modern telephone. The wiring is also non-standard and may tinkle bells on your premises, when dialling out.

  1. Red of new line cord to Terminal 1.
  2. Remove any link between Terminals 2 and 3.
  3. Insert 3.3k resistor between Terminals 2 and 3.
  4. White of new line cord to Terminal 2.
  5. Connect the Rectifier Element across the earpiece terminals.  If the phone goes faint then remove the it.


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Last revised: September 19, 2019