GEC
MURAPHONE CONVERSION TO PST

There are two types of Muraphone, the Muraphone and the Muraphone K.  The easiest way to identify them is to check the handset cord - 3 wires original Muraphone and with 4 wires it is the Muraphone K.  The original Muraphone has the GPO style handset with a spittoon mouthpiece, whilst the Muraphone K has a modern curved handset.
 

Conversion of the early Muraphone (wired to diagram KS10267)
The terminal layout of the phone is shown below - the terminals are marked in the plastic.

Using a standard BT line cord wire the phone as follows:-

1. Remove any link between E and L1.

2. White wire of new line cord to terminal L1.

3. Red wire of new line cord to terminal L2.

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

5. Disconnect red wire on the 2uf capacitor.

6. Connect the blue wire of the new line cord to the red wire and insulated.

7. Fit a 3.3k ohm resistor between E and L1.

8. Fit a Rectifier Element No. 205 between MR and R.

9. Check transmission and replace transmitter if bad.  Click here for more information.

Diagram KS10267

Conversion of the later Muraphone K (wired to diagram KS10992 Issue C)
The terminals are marked on the terminal block.

Using a standard BT line cord wire the phone as follows:-

1. Remove the strap between 11 and 12.
2. Connect the 3.3k resistor between 11 and 12.
3. White wire of the new line cord to 12.
4. Remove the strap between 13 and 14.
5. Red wire of the new line cord to 14.
6. Blue wire of the new line cord to 4.
7. Green wire of the new line cord to 3.
8. Fit a Rectifier Element No. 205 between 1 and 9.

Diagram KS10992C

Last revised: October 14, 2022