CONVERTING OLD TELEPHONES
TO THE UK PLUG AND SOCKET SYSTEM


Click here on where to obtain a telephone line cord (conversion kit)

Click here on where to obtain replacement braided telephone cords

UK cord wire colours to Non -UK cord wire colours converter

Click here for instructions on how to fit an electronic Transmitter and Rectifier Element No. 205

Click here to view a fully converted Telephone No. 706 and No. 746 - also applicable to all 700 type telephones

Click here on how to wire up sockets

Non UK phone to UK conversion

Onyx Telephones - Italian phones with a square circuit board inside

Basic fault finding on your telephone and issues after converting

Around 1979, Post Office Telephones introduced the Plug and Socket (PST) method of connection.  This document explains how to convert many old British telephone instruments to PST working.  The following information assumes that a standard new plan BT line cord (light grey, flat plastic (ridge on one flat) with a flat plug one end and spades the other) is used.  Do not attempt to fit a new style plug to the old style round PVC or cloth telephone line cord - this usually fails - buy the correct cord or similar.

If your replacement cord has no grommet (grommets were only used on 700 type telephones) just slit the original grommet with a sharp knife, pull out the old cord, insert the new cord with a blob of glue and refit into phone.  The original 200 and 300 type telephone line cords were restrained by a cotton tie.  For these phones just insert the replacement line cord into the telephone and tie a knot in it (the latest replacement cords have grommets on them - these will stop the cable from pulling out).

Strap or Link
There are references to strapping and straps in the text below.  This refers to the metal links that connect two terminals together. They can be removed by releasing the screws that hold them captive - always tighten the screws again afterwards as they have a tendency to fall out. In some instances these straps are replaced by wire and in fact a strap can be a piece of wire.

Terminal Numbering
There are also references below to T and B numbers.  T1 would mean terminal 1 in the telephone, whilst B2 would mean terminal 2 in the Bellset.  Any other letters will be self evident.

The cord colours used by BT are shown below and are used throughout this page.  If you are not using a standard BT cord then click here.

BT CORD COLOURS:- R = RED, W = WHITE, B = BLUE, G = GREEN

The conversions below assume that the original telephone line cord will be discarded and replaced with a modern line cord.

Converting an old GPO telephone does not make it approved and therefore it cannot be legally connected to any Telecom network in the UK.

Always fit a rectifier unit (Rectifier Element No. 205) across the earpiece of a converted telephone (stops acoustic shock) and because the original carbon granule transmitters are generally noisy or faint it is also advisable to change them to a modern electronic type (these are a direct replacement for 700 type transmitters and can be modified to fit in Bakelite handsets).


UK Telephone Conversions

GPO/PO/BT Telephone Conversions


GPO Telephone 1

Telephone is wired to standard diagram (N101). This telephone does not lend itself to proper conversion, but can be adapted as follows:-

  1. Remove strap between terminals L1 and E and replace with a 3.3k ohm resistor.
  2. White wire of new line cord to terminal L1.
  3. Red wire of new line cord to terminal L2.
  4. Green and blue wires of new line cord are insulated with tape (not used).

GPO Telephone 11

Telephone is wired to standard diagram (N111). This telephone does not lend itself to proper conversion, but can be adapted as follows:-

  1. Remove strap between terminals G and EB and replace with a 3.3k ohm resistor.
  2. White wire of new line cord to terminal A.
  3. Red wire of new line cord to terminal B.
  4. Connect two D type batteries in series and connect the positive of the batteries to the + terminal (red wire) and the negative of the batteries to the - terminal (red/white wire).  The D batteries should be fitted in a proper battery holder.
  5. Blue wire of the new line cord to terminal G.
  6. Remove the orange/white wire from terminal 3 of the generator.
  7. Green wire of new line cord is insulated with tape (not used).

GPO Telephone 121

Telephone is wired to standard diagram (N221) but modified as follows:-

Telephone with numbered terminals:-

  1. White of new line cord to terminal 4.
  2. Remove strap between terminals 4 and 6 and insert a 3.3k ohm resistor  between terminals 4 and 6 (the link may a piece of wire soldered to the terminals).
  3. Red of new line cord to terminal 8.
  4. Blue of new line cord to terminal 3.
  5. Disconnect one wire from the capacitor and insulate.
  6. Green of new line cord - insulate with tape (not used).
  7. Terminals 2 and 5 should be linked already - check on this.
Telephone with lettered terminals:-
  1. Disconnect  the Green/white wire on the capacitor.
  2. Connect the blue line cord wire to the green/white wire and insulate.
  3. Remove the strap between L1 and E (this may be soldered under the terminal strip).
  4. Insert a 3k3 resistor between L1 and E.
  5. Connect the white line cord wire to L1.
  6. Connect the red line cord wire to L2.
  7. Insulate the green line cord wire.

GPO Telephone 150 with Bellset No. 1 or Bellset 25

Telephone is wired to standard diagram (N250) which includes the Bellset but modified as follows:-

  1. Telephone cord - White - wired between terminal T in phone and terminal L2 in a Bellset No. 1.
  2. Telephone cord - White - connect directly to Red of new line cord in a Bellset No. 25.  Use a small nut and bolt and then cover with insulation tape.
  3. Telephone cord - Red - wired between terminal TR in phone and terminal TR in Bellset.
  4. Telephone cord - Green - wired between terminal R in phone and terminal R in Bellset.
  5. White of new line cord to terminal L1 in Bellset.
  6. Remove strap between terminal L1 and terminal E and insert a 3.3k ohm resistor.
  7. Remove the terminal T - L2 metal strap in the Bellset No. 1.  There is a soldered strap in a Bellset No. 25, behind the terminal plate, in this instance leave the strap in place.
  8. Red of new line cord to terminal L2 in a Bellset No. 1.
  9. Blue of new line cord to terminal T in Bellset.
  10. Short out the two terminals of the capacitor with a piece of bare wire.
  11. Green of new line cord - insulate with tape (not used).

To disconnect bell (if needed)
Remove strap between L1 and E or leave out the resistor.

Dial terminations
The dial on a Telephone No. 150 is wired as follows:-

  • Dial terminal 1 to telephone terminal D using the blue wire of the dial cord.
  • Dial terminal 2 to telephone terminal R using the grey wire of the dial cord.
  • Dial terminal 3 to telephone terminal TS using the brown wire of the dial cord.
  • Dial terminal 4 to telephone terminal TD using the pink wire of the dial cord.
  • Dial terminal 5 to telephone terminal T using the orange wire of the dial cord.

GPO Telephone 156 using a Bellset No. 1 or Bellset 25

Telephone is wired to standard diagram (N256) which includes the Bellset but modified as follows:-

  1. Remove the link between 7 and 4 in the phone.
  2. Telephone cord - White - wired between 2 in phone and L2 in a Bellset No. 1.
  3. Telephone cord - White - connect directly to Red of line cord in a Bellset No. 25.  Use a small nut and bolt and then cover with insulation tape.
  4. Telephone cord - Red - wired between 3 in phone and TR in Bellset.
  5. Telephone cord - Green - wired between 6 in phone and R in Bellset.
  6. White of new line cord to L1 in Bellset.
  7. Remove strap between L1 and E and insert a 3.3k ohm resistor.
  8. Remove the T - L2 metal strap in the Bellset No. 1.  There is a soldered strap in a Bellset No. 25, behind the terminal plate, in this instance leave the strap in place.
  9. Red of new line cord to L2 in a Bellset No. 1.
  10. Blue of new line cord to T in Bellset.
  11. Short out the two terminals of the capacitor with a piece of wire.
  12. Green of new line cord - insulate with tape (not used).

To disconnect bell (if needed)
Remove strap between L1 and E or leave out the resistor.


GPO Telephone 162

Telephone is wired to standard diagram (N262) which includes the Bellset No. 1 or 25 but modified as follows:-

  1. Remove strap T - L2, which is under the Bellset terminal board.
  2. Telephone cord - White - between 3 in phone and T in Bellset.
  3. Telephone cord - Red - between 1 in phone and TR in Bellset.
  4. Telephone cord - Green - between 2 in phone and R in Bellset.
  5. White of line cord to L1.
  6. Remove strap between E and L1 and insert a 3.3k ohm resistor.
  7. Red of line cord to L2 - move the white wire of the telephone cord from T to L2.
  8. Blue of line cord to T - short out the two terminals of the capacitor.
  9. Green of line cord - insulate with tape (this wire is not used).

To disconnect bell (if needed)
Remove strap between L1 and E or leave out the resistor.


GPO Telephone 1/196

Telephone is wired to standard diagram (N296) but reference to the full wiring diagram must be made for connection to a Bellset No. 31(N1297).
This telephone is designed for use on Local Battery circuits and therefore a battery is used to power the transmitter.  A 1.5 volt battery should be connected to the Bellset (a U2 battery is suggested).

Conversion using a Telephone No. 1/196 and Bellset No. 31 is as follows:-

  1. Orange of cord between Telephone and Bellset - T2 connects to B1.
  2. Green of cord between Telephone and Bellset - T4 connects to B5.
  3. Red of cord between Telephone and Bellset - T1 connects to B4.
  4. White of cord between Telephone and Bellset - T3 connects to B2.
  5. Install Battery to Bellset terminals B4 and B3 with positive connected to B3.
  6. Telephone line cord - White - to B6 in Bellset.
  7. Telephone line cord - Red - to B8 in Bellset.
  8. Telephone line cord - Blue -  to B1 in Bellset.
  9. Telephone line cord - Green - not used so just insulate.
  10. Remove one of the wires from the capacitor and insulate.
  11. Insert a 3.3k resistor between B6 and B7 in the Bellset (these terminals may be linked by a soldered wire on the rear of the terminal block.  Remove this link if it exists.

GPO Telephone 221

Telephone is wired to standard diagram (N321) which includes the Bellset but modified as follows:-

Telephone with numbered terminals:-

  1. Disconnect the green/white wire from the capacitor.
  2. Connect the green/white to the blue wire of the line cord and insulate.
  3. Remove the strap between terminals 6 and 7.
  4. Insert a 3.3k resistor between terminals 6 & 7.
  5. White of the line cord to terminal 6.
  6. Red of the line cord to terminal 9.
Telephone with lettered terminals:-
  1. Disconnect and sleeve the Green wire that is on TR (it goes to terminal 2 of the Induction Coil and is not needed).
  2. Move the Orange wire from the Condenser that is on L2 - onto TR.
  3. Wire the Condenser tags together (square metal box).
  4. Remove the strap between L1 and E (this may be soldered under the terminal strip).
  5. Insert a 3k3 resistor between L1 and E.
  6. Connect the white line cord wire to L1.
  7. Connect the red line cord wire to L2.
  8. Connect the blue line cord wire to TR.

GPO Telephone 232

Telephone is wired to the standard diagram (N332) but modified as follows:-
(B = Bellset terminal & T = Telephone Terminal).

With Bellset No. 26 and using the original cloth cord between the telephone and Bellset.

  1. Remove Bellset strap B4 - B5.
  2. Remove Bellset strap B2 - B3.
  3. Insert a 3.3k ohm resistor between B2 and B3.
  4. Ensure that Bellset strap B7 - B8 is in place.
  5. Wire the cords as per the table below.
  6. Green of the line cord is not used - insulate with tape.

With Bellset No. 31 and using the original cloth cord between the telephone and Bellset.

  1. Remove Bellset strap B6 - B7.
  2. Connect 3.3k resistor between Bellset E and B9.
  3. Wire the cords as per the table below.
  4. Green of the line cord is not used - insulate with tape.

With Bellset No. 41 and using the original cloth cord between the telephone and Bellset.

  1. Remove Bellset strap B8 - B9.
  2. Remove Bellset strap B6 - B7.
  3. Remove Bellset strap B2 - B4.
  4. Connect 3.3k resistor between Bellset B5 and B8.
  5. Wire the cords as per the table below.
  6. Green of the line cord is not used - insulate with tape.

The table below advises of the cord termination

Telephone - Cord - Bellset - Line Cord

Telephone
Terminals
Wire colours of old cloth cord from phone to bellset Bellset 26
Terminals
Bellset 31
Terminals
Bellset 41
Terminals
Wires colours of new style plastic line cord
T3 White wire to B5 B4 B4 Red wire
T1 Red wire to B7 B7 B5 White wire
T2 Green wire to B3 B1 B9 Blue wire

Without any Bellset and not using the original cloth cord between the telephone and Bellset (New style line cord directly connected phone).

  1. Red of line cord to T3.
  2. White of line cord to T1.
  3. Blue of line cord to T2.
  4. Green of line cord is not connected - insulate with tape.

GPO Telephone 246

Telephone is wired as follows.  The standard diagram for the Phone is N326 and the wiring Diagram for the phone and Bellset No. 37 is N4299.  (B = Bellset terminal & T = Telephone Terminal).

  1. Red of line cord to B6.
  2. White of line cord to B8.
  3. Blue of line cord to BE.
  4. B8 wired to T8.
  5. B1 wired to T9.
  6. If no dial is fitted then wire B6 to B4 and T7.
  7. B9 wired to T2.
  8. BE wired to T1.
  9. B3 wired to T6.
  10. B2 wired to T5.
  11. Remove the soldered wire link between B7 and B8 - it is under the board.
  12. Wire a 3.3k Resistor between B7 and B8 (leave out if bell not to be connected).
  13. Remove the white wire from Capacitor and insulate the end.

If dial is fitted:-

  1. Remove link between B4 and B6.
  2. Leave T7 wired to B4.
  3. Dial 1 and Dial 3 terminals to B5.
  4. Dial 2 to B1.
  5. Dial 4 to B4.
  6. Dial 5 to B6.

GPO Telephone 248 and Bellset No.39A

This method of wiring is only applicable for the base unit and no extension phones may be wired from the Bellset.  The Bellset switch should be left in the speak to exchange position.  There are no bells in any of these Bellsets.

Telephone and Bellset are wired to follows (no bells are fitted):-

  1. T3 to B19 and B20 - black of connecting cord.
  2. T9 to B23 and B24 - pink of connecting cord.
  3. T10 to B17 - brown of connecting cord.
  4. T11 to B16 - grey of connecting cord.
  5. T1 to B15 - blue of connecting cord.
  6. Remove link B13 to B14.
  7. Move the orange of connecting cord from B18 to B14 - the other end is connected to T2.
  8. Blue of the line cord to B14.
  9. White of the line cord to B1.
  10. Red of the line cord to B3 and B4.
  11. Green of the line cord - insulate - not used.

GPO Telephone 248 and Bellset No.44

Telephone and Bellset are wired to follows (no bells are fitted):-

  1. T3 to B34 and B35 - black of connecting cord.
  2. T9 to B31 - pink of connecting cord.
  3. T10 to B26 - brown of connecting cord.
  4. T11 to B25 - grey of connecting cord.
  5. T1 to B19, B20 and B21 - blue of connecting cord.
  6. Remove any links between B13 and B14.
  7. Remove any links between B17 and B18.
  8. Move the orange of connecting cord to from B27 to B14 - the other end is connected to T2.
  9. Blue of the line cord to B14.
  10. White of the line cord to B1 and B2.
  11. Red of the line cord to B3 and B4.
  12. Green of the line cord - insulate - not used.

GPO Telephone 306

Telephone is wired as follows. The standard diagram is N406.

  1. Remove strap T10 - T11.
  2. Remove any wire or straps connected to T2, T3, T7, T12 or T13.
  3. Do not fit a 3.3K ohm resistor as this telephone does not have a magneto bell.
  4. Insert strap T8 - T9.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 308

Telephone is wired as follows. The standard diagram is N408.

  1. Remove strap T10 - T11.
  2. Strap T11 - T12.
  3. Install a 3.3K ohm resistor between T1 and T2.
  4. Strap T8 - T9.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 310

Telephone is wired as follows. The standard diagram is N410.

  1. Remove strap T10 - T11.
  2. Strap T11 - T12.
  3. Install a 3.3K ohm resistor between T1 and T2.
  4. Insert strap T1 - T9.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 311

Telephone is wired as follows. The standard diagram is N411.

  1. Remove strap T10 - T11.
  2. Insert strap T11 - T12.
  3. Install a 3.3K ohm resistor between T1 and T2.
  4. Insert strap T1 - T7.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T3.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 312

Telephone is wired as follows. The standard diagram is N412.

  1. Remove strap T10 - T11.
  2. Remove strap T12 - T13.
  3. Insert a 3.3K ohm resistor between T11 & T12.
  4. Link all the following terminals together T1 - T2 - T3 - T9.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 314

Telephone is wired as follows. The standard diagram is N414.

  1. Remove strap T10 - T11.
  2. Remove strap T12 - T13.
  3. Install a 3.3K ohm resistor between T11 and T12.
  4. Insert strap T7 - T2.
  5. Red of line cord to T8.
  6. White of line cord to T7.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T9.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

Bell On/Off switch - Please refer to Diagram N4301 for additional information.

There are many types of switches that could be used so check the number of the switch unit and wire accordingly.

  1. Remove all switch wires from the telephone terminals.
  2. Wire the phone as above, but omit the strap between T7 - T2.
  3. On Key No.s 302A and 302B, with the locking rotating switch, connect red wire from the switch T7 and the green wire from the terminal to T2.
  4. On a Key No. 303A, with the the left hand key that locks down, connect with wire switch terminal 27 to T7 and switch terminal 25 to T2.
  5. On a Key No. 304A, with the the left hand key that locks down, connect with wire switch terminal 10 to T7 and switch terminal 12 to T2.
  6. On a Key No. 304B, with the the left hand key that locks down, connect with wire switch terminal 11 to T7 and switch terminal 12 to T2.
  7. Insulate any other wires from the switch from the switch that cannot be removed.

GPO Telephone 321

Telephone is wired as follows. The standard diagram is N421.  If this telephone is wired with a switch, thermistor and diode then remove these items and follow the instructions below.

  1. Remove strap T10 - T11.
  2. Remove strap T12 - T13.
  3. Install a 3.3K ohm resistor between T12 and T13.
  4. Insert strap T11 - T12.
  5. Strap T1 - T2, T8 and T2.
  6. Red of line cord to T3.
  7. White of line cord to T1.
  8. Blue of line cord to T11.
  9. Green of the line cord is spare and can be parked on T9.
  10. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 326

Telephone is wired as follows. The standard diagram is N426.
This telephone has no ringer that will work on an exchange line, so your phone will not ring.

  1. Remove strap T10 - T11.
  2. Remove any wire or straps connected to T2 or T12.
  3. Do not fit a 3.3K ohm resistor as this telephone does not have a magneto bell.
  4. Insert strap T8 - T9.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 327

Telephone is wired as follows. The standard diagram is N427.

  1. Remove strap T10 - T11.
  2. Remove any wire or straps connected to T2 or T12.
  3. Do not fit a 3.3K ohm resistor as this telephone does not have a magneto bell.
  4. Insert strap T8 - T9.
  5. Red of line cord to T8.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone 328

Telephone is wired as follows.  The standard diagram is N428.

  1. Remove strap T10 - T11.
  2. Insert strap T8 - T9.
  3. Insert strap T1 - T2.
  4. Insert a 3.3K ohm resistor between T11 & T12.
  5. Red of line cord to T9.
  6. White of line cord to T1.
  7. Blue of line cord to T11.
  8. Green of the line cord is spare and can be parked on T7.
  9. Rectifier No. 205 (if needed) inserted between T6 & T5.

Bell On/Off switch - Please refer to Diagram N4301 for additional information.

Bell switch not needed - phone will always ring

  1. Remove all switch wires from the telephone terminals and insulated with tape.  Wire telephone as above.

Bell switch needed - switch will disconnect bell from ringing - there are many types of switches that could be used so check the number of the switch unit and wire accordingly.

  1. Remove all switch wires from the telephone terminals.
  2. Wire the phone as above, but omit the strap between T1 - T2.
  3. Generic instructions - Connect one wire of switch to T1 and the other wire of switch to T2.
  4. On Key No.s 302A and 302B, with the locking rotating switch, connect red wire from the switch T1 and the green wire from the terminal to T2.
  5. On a Key No. 303A, with the the left hand key that locks down, connect with wire switch terminal 27 to T1 and switch terminal 25 to T2.
  6. On a Key No. 304A, with the the left hand key that locks down, connect with wire switch terminal 10 to T1 and switch terminal 12 to T2.
  7. On a Key No. 304B, with the the left hand key that locks down, connect with wire switch terminal 11 to T1 and switch terminal 12 to T2.
  8. Insulate any other wires from the switch from the switch that cannot be removed

GPO Telephone 330, 332 & 333

Telephone is wired as follows.  The standard diagrams are N430, N432 & N433.

  1. Remove strap T10 - T11.
  2. Remove strap T11 - T12.
  3. Insert strap T8 - T9.
  4. Insert strap T1 - T2.
  5. Insert a 3.3K ohm resistor between T11 and T12.
  6. Rectifier No. 205 (if needed) inserted between T6 & T5.
  7. Red of line cord to T9.
  8. White of line cord to T1.
  9. Blue of line cord to T11.
  10. Green of line cord to T3.

GPO Telephone 394

This is a special telephone and only works with local battery.  To this end the phone cannot be wired exactly to UK standards and because of this you may find that when this phone dials out, other phones in the house tinkle.  I suggest that two AA batteries be fitted inside the telephone.  The standard diagram is N494.

  1. Insert a strap between T6 and T7.
  2. Insert a 3.3K ohm resistor between T1 and T2.
  3. Rectifier No. 205 (if needed) inserted between T6 & T5.
  4. Red of line cord to T11.
  5. White of line cord to T1.
  6. Blue of line cord to T6.
  7. Green of line cord to T3.
  8. Battery to T10.
  9. Battery to T9.

GPO Telephone 706, 710, 741 & 746

Telephone is wired as follows. The standard diagrams are (N806, N810, N841 & N846).

The bell or ringing device should be 4000 ohms resistance.  This can be rectified by either fitting the correct ringer or by inserting a 3.3K resistor in series with the ringer.  The telephone should already be fitted with a Rectifier No. 205.  If one is not fitted then it is recommended that one is fitted.

  1. Remove strap T6 - T7.
  2. Remove strap T4 - T5.
  3. Insert strap T5 - T6.
  4. Red wire of line cord to T8.
  5. Blue wire of line cord to T6.
  6. Insert straps T16 - T17 - T18 - T19.
  7. White wire of line cord to T18.
  8. Green wire of line cord to T15.
  9. Insert a 3.3K resistor between T4 - T5 (object with coloured stripes on it).
  10. Insert a Rectifier No. 205 (if needed) between T1 and T2.

The original BT line cord is called a Cord Connecting No 4/502

Bell On/Off switch
To fit a bell on/off switch obtain and fit the following items:-
(746 style phones need 2 pins, On/Off button and Switch No. 23A, whilst 706 phones need Switch No. 5A and the appropriate coloured On/Off button).

Wire and install as follows:-

  1. Remove strap T16 - T17 only.  Leave T17-T18 and T19 in place with the white of the line cord.
  2. Connect Brown wire of switch to T16.
  3. Connect Grey and Blue wires of the switch to T17.

Telephone No. 706 switch installation

  1. Remove plastic blank plate from top of telephone case, by sliding the metal clip to one side.
  2. Remove one of the screws that fixes the switch to the bracket.
  3. Slacken off the other screw.
  4. Slide the bracket round so that the plastic button can locate between the switch and the bracket.
  5. Slide the switch back into position and insert the screws.
  6. Fit the switch to the phone by first ensuring that the fixing screw is unscrewed at least 3/8th inch.
  7. Then offer the switch to the phone at an angle and engage the lug.
  8. Drop the other end of the switch down and fix by means of the single screw.

Telephone No. 710, 740 and 746 switch installation

  1. Remove plastic blank plate from top of telephone case by pushing outwards from inside the case.
  2. Offer the button into the opening so that the slots in button line up with slots inside casing.
  3. Insert one pin so that it goes through the button and rests on the two slots inside the case.
  4. Push the pin into the slots.
  5. Repeat steps 3 & 4 for the other pin.
  6. The switch is located centrally between the switch hooks.
  7. Install the white nylon spring plunger by firstly pushing it down against the spring into the middle slot between the switch hooks.
  8. Whilst depressing the plunger push towards the front of the phone until the triangular lug locates in the vertical slot.
  9. Release the plunger and it rise slightly and then stop.
  10. Then locate the switch, over the plunger and to one side, with the lug towards the front of the phone and just above the metal work.
  11. Whilst pushing the switch against the white plunger, slide the switch down until the bottom locates into the bottom of the switch hook mounting and the lug at the top locates in the top of the mounting.
  12. The white plunger can now be depressed.  It should operate the switch with an audible click and then spring back by itself.

GPO/PO Telephone 722, 766 & 786 (Trimphone)

Telephone is wired as follows. The standard diagrams are (N822, N866 & N886).

The bell or ringing device should be 4000 ohms resistance.  This is achieved by inserting a 3.3K resistor between T4 & T5.  It is sometimes preferable to not wire a Trimphone ringer up.  This is because it can sometimes upset the rest of your telephone ringers.  The Trimphone volume control has an Off position, which is obtainable by removing the case and slackening off the screw on top of the volume control switch itself.

  1. Remove strap T6 - T7.
  2. Remove strap T4 - T5.
  3. Insert strap T5 - T6.
  4. Connect red wire of line cord to T8.
  5. Connect blue wire of line cord to T6.
  6. Insert straps T16 - T17 - T18 - T19.
  7. Connect white wire of line cord to T18.
  8. Connect green wire of line cord to T15.
  9. Insert a 3.3K resistor between T4 - T5.

The original BT line cord is called a Cord Connecting No 4/504.


GPO/PO Telephone 745

Telephone is wired as follows. The standard diagram is N845.

The bell or ringing device should be 4000 ohms resistance.  This can be rectified by either fitting the correct ringer or by inserting a 3.3K resistor in series with the ringer.  The telephone should already be fitted with a Rectifier No. 205.  If one is not fitted then it is recommended that one is fitted.  If no dial is fitted then terminals T9 - T10 should be linked.

  1. Remove strap T6 - T7.
  2. Remove strap T4 - T5.
  3. Insert strap T5 - T6.
  4. Red wire of line cord to T8.
  5. Blue wire of line cord to T6.
  6. Insert straps T16 - T17 - T18 - T19.
  7. White wire of line cord to T18.
  8. Green wire of line cord to T15.
  9. Insert a 3.3K resistor between T4 - T5.
  10. Insert a Rectifier No. 205 (if needed) between T1 and T2.

The original BT line cord is called a Cord Connecting No 4/502


GPO/PO Telephone 776 (Compact) and Jubilee Compact

Telephone is wired to standard diagram (N876) but modified as follows:-

Telephone No. 776 and Jubilee without Bellset

  1. Remove strap T2 - T3.
  2. Insert strap T1 - T2.
  3. Blue of line cord to T1.
  4. Red of line cord to T4.
  5. White of line cord to T5.
  6. Green of line cord to T6.

Telephone No. 776 with Bell Unit No. 776 (using original cord between Telephone and Bellset)

  1. Remove strap T2 - T3.
  2. Insert strap T1 - T2.
  3. Insert strap B1- B2 - B3.
  4. Remove strap B5 - B6.
  5. Insert 3.3k resistor between B5 and B6.
  6. Connect the cords as detailed in the table below (any colours in the original cord not mentioned below should be not used and insulated with tape.
Telephone Original cord Bellset New line cord
T4 - Red - B4 - Red
T1 - Blue - B5 - Blue
T5 - White - B1 - White
T7 - Green - B2 - Green not connected

Jubilee and Telephone SA4271 with Bellset Bell Unit SA4271 (using original cord between Telephone and Bellset).

In the instructions below the T refers to the telephone terminals 1 to 9.  Please disregard the handset terminals T1 & T2.

  1. Bellset terminals L1, L2 and E are not used in these instructions and nothing should be connected to them.
  2. Remove strap T2 - T3.
  3. Insert strap T1 - T2.
  4. Ensure that no strap exists between B2 and B3.
  5. Insert straps between B5 - B6 - B7.
  6. Remove strap B3 - B4.
  7. Insert 3.3k resistor between B3 and B4.
  8. Connect the cords as detailed in the table below.
Telephone Original cord Bellset New line cord
T4 - Red - B1 - Red
T1 - Blue - B3 - Blue
T5 - White - B7 - White
T9 - Black - B4    
T8 - Orange - B5    
T7 - Green - B6    
Green not connected

GPO/BT TELEPHONE SPECIAL RANGE (TSR)

TSR 1001 (Mickey Mouse)

  1. Remove black and grey wire links (if they exist).
  2. Link terminals 1, 2 and 9.
  3. Connect one wire of the ringer to terminal 7.
  4. Connect other wire of the ringer to terminal 9.
  5. Connect 3.3k resistor to terminals 5 and 7.
  6. Connect the white wire of the line cord to terminal 5.
  7. Connect the red wire of the line cord to terminal 4.
  8. Connect the blue wire of the line cord to terminal 2.

TSR 1002 (Contempra)

TSR terminals Y X G L1 L2
Cord Inst 4/502 - B G R W

Notes:

  1. Remove existing line cord.
  2. Cut off grommet from new cord 4/502.
  3. Connect new cord 4/502 to terminals as shown above and secure cord.
  4. Fit a Thermistor 1a-1 between terminals 1 & 4 (if no terminal 4 appears on PCB then the Thermistor should be fitted between terminals G & Y).


Old method - not recommended

TSR terminals Y X G L1 L2
Cord Inst 4/502 - R W G B

TSR 1003 (Astrofon)

TSR terminals 9 8 7 6 5 4 3 2 1
Cord Inst 4/502       B   G R W  

Notes:

  1. Remove existing line cord and connect new Cord 4/502 to terminals as shown above.
  2. Secure new cord and fit Thermistor 1A-1 between terminals 2 & 5.

TSR 1004 (Ericofon 700)

TSR terminals - 1 - 2 3 B R 4 5 W
  - 6 G 7 8 - - 9 10 -

Notes:

  1. Remove existing cord.
  2. Remove grommet from new cord 4/502 and connect as shown above.
  3. Link W to the point below but to the right of 10.
  4. Secure new cord.

TSR 1009 (Eiger)

TSR terminals 2 3 4
Cord Inst 4/502 R W -

Notes:

  1. Remove existing line cord and remove grommet.
  2. Remove the ends of the spade connectors on new Cord 4/502.
  3. Solder the stumps to the TSR terminals as shown above.
  4. Secure new cord 4/502 by modification of existing grommet.
  5. Solder a Thermistor 1a-1 to terminals 3 & 4.

TSR 1000 (Classic)

TSR terminals 19 18 17 16 15 11 10 9 8 7 6 5 4
Cord Inst 4/502   W   G       R     B    

Notes:

  1. Remove existing line cord and remove grommet.
  2. Remove grommet from new Cord 4/502 and connect to terminals as shown above.
  3. Secure line cord internally by re-utilisation of existing grommet.
  4. Fit a thermistor 1a-1 between terminals 17 & 18.

TSR 1007 (Ericofon 600)

TSR terminals 1         8
  2 3 3 5 6 7
Cord Inst 4/502   R   W    

Notes:

  1. Remove existing line cord.
  2. Remove grommet from new cord 4/502 and connect to terminals as shown above.
  3. Secure new cord internally.

Other GPO Apparatus


LOUDSPEAKING TELEPHONE No. 4D (Diagram N4475)

This telephone is powered by a 50 volt DC power supply.  It is not allowable to wire this via the line jack.  On the end of the LST line cord fit a six way junction box - the phone was originally fitted with a Block Terminal No. 36A.  Connect a new style line cord and the power supply to this junction box.

  1. Remove strap T8 - T9.
  2. Remove strap T4 - T5.
  3. Insert strap T5 - T6.
  4. Red wire of old line cord to T8.
  5. Blue wire of old line cord to T6.
  6. Insert straps T16 - T17 - T18 - T19.
  7. White wire of old line cord to T18.
  8. Green wire of line cord to T13.
  9. Insert a 3.3K resistor between T4 - T5.
  10. + terminal connects the orange wire of the old line cord.
  11. - terminal connects to the black wire of the old line cord.
  12. In the junction box, connect the red wire of the old cord to the red wire of the new line cord.
  13. In the junction box, connect the white wire of the old cord to the white wire of the new line cord.
  14. In the junction box, connect the blue wire of the old cord to the blue wire of the new line cord.
  15. In the junction box, connect the green wire of the old cord to the green wire of the new line cord.
  16. In the junction box, connect the orange wire of the old cord to the positive terminal of the power unit.
  17. In the junction box, connect the black wire of the old cord to the negative terminal of the power unit.
  18. Ensure that the power wires do make contact with any other wires.

GPO/PO Planset N625

These instructions are for the Planset only and not when any extensions are fitted.

These instructions assume that the Planset and attached phone are correctly wired to N4509 already.

  1. Red wire of line cord to Block terminal 4.
  2. White wire of line cord to Block Terminal 6.
  3. Blue wire of the line cord to Block terminal 5.
  4. Replace the link between Planset terminals 6 and 7 with a 3.3k resistor.
  5. In the telephone remove the capacitor connected to terminals 13 and 14.
  6. In the telephone remove the link between terminals 6 and 7.
  7. In the telephone link terminals 4, 5 and 6 together.  Leave any connected wires on these terminals.
  8. In the telephone connect a piece of wire to Terminal 5 and run this wire into the Planset base. You will have to slacken or remove the three screws that fix the telephone to the base, so that the wire can be fed through.
  9. In the Planset base remove the cord wire from Terminal 5. It should be orange/white in colour.
  10. Connect the wire that was run 8 above, to the orange/white cord wire and insulate.

These instructions are for when the Planset is wired up with extensions.

The extensions should be wired directly to the Planset Block Terminal.  This is not a pure conversion and you may find that when dialling out other phones connected to PST sockets tinkle.

  1. Wire the Planset and extension phones as per the relevant diagram (N4507 or N4509).
  2. Red wire of line cord to Block terminal 4.
  3. White wire of line cord to Block Terminal 6.
  4. Insulate the blue and green wires as they are not used.

 


Non UK Telephone Conversions

The phones below are listed in alphabetical order depending on Manufacturers Name.  The line cord replacement in all the conversions below is the UK PST cord with the flat white plug.

Bell Manufacturing Co. - Diagram ST132 (Click here for diagram ST132)

  1. Remove original line cord.
  2. Red of the line cord to terminal B.
  3. Remove the link between terminals A and S.
  4. Insert 3.3k resistor between terminals A and S.
  5. White of the line cord to terminal A.
  6. Remove the single wire (sometimes two wires on some phones) from the 1 uf capacitor (grey metal canister).  These wires are be on the terminal nearest the base plate.
  7. Connect blue of the line cord to the wire that has just been removed and insulate.
  8. Insulate the green wire of the line cord.

 

Dutch PTT T65
The circuit board build of this model phone does not allow for an easy conversion.  The details here will work, but if multiple bells are on the system then there may be difficulties. Try converting using 1 to 7 firstly.  If this works then just insulate the blue line cord wire.  If you have problems then follow all the instructions.

  1. Remove original line cord.
  2. Connect red of the line cord to 1.
  3. Connect white of the line cord to 3.
  4. Do not connect the blue of the line cord.
  5. Connect a 3.3k resistor to 3 and 4.
  6. Insulate the green wire of the line cord.
  7. Test the phone and if it works OK - stop here.
  8. If you phone has problems then carry on.
  9. Locate the capacitor - it is towards the front of the circuit board.
  10. Looking from the front, cut the lead on the right hand side of the capacitor, in the middle.  Leave enough to reconnect if necessary.
  11. Bend the piece of lead that is connected to the capacitor out of the way.
  12. Solder the blue of the line cord to the wire that is still in the circuit board.

 

Ericsson Dialog (table or wall) (Click here for diagram)
The circuit board build of this model phone does not allow for a complete conversion.  The details here will work, but if multiple bells are on the system then there may be difficulties. If you have problems with bells then leave out the resistor in which case the bell on this phone will not ring.

  1. Remove original line cord.
  2. Remove any link found between terminals 3 and 4.
  3. Connect a 3.3k resistor to terminals 3 and 4.
  4. Connect red of the line cord to terminal 2.
  5. Connect white of the line cord to terminal 3.
  6. Insulate the blue and green wires of the line cord.


 

Ericsson Type 1951 (Click here for diagram 31343)

  1. Remove original line cord.
  2. Connect Red of the line cord to terminal 9.
  3. Remove any link found between terminals 10 and 11.
  4. Insert 3.3k resistor between terminals 10 and 11.
  5. Connect White of line cord to terminal 10.
  6. Remove the blue wire from capacitor C1 (grey oblong object).
  7. Connect blue of the line cord to the blue wire which was removed above and insulate.
  8. Insulate the green wire of the line cord.

This conversion is for both the Type 1951 wall and Desk models


Ericsson DBH 160 1616
(Click here for diagram 361677)

  1. Remove original line cord.
  2. Red of the line cord to terminal 10.
  3. Remove the link between terminals 6 and 8.
  4. Insert 3.3k resistor between terminals 6 and 8.
  5. White of the line cord to terminal 8.
  6. Remove the yellow wire from the capacitor C1 terminal.
  7. Connect blue of the line cord to the yellow wire which was removed above and insulate.
  8. Insulate the green wire of the line cord.


Ericsson DBN 1555 58
(Click here for diagram 429270)

  1. Remove original line cord.
  2. Red of the line cord to terminal 10.
  3. Remove the link between terminals 6 and 8.
  4. Insert 3.3k resistor between terminals 6 and 8.
  5. White of the line cord to terminal 8.
  6. Remove the yellow wire from the capacitor C1 terminal.
  7. Connect blue of the line cord to the yellow wire which was removed above and insulate.
  8. Insulate the green wire of the line cord.


French PTT Model 24 (Mother-in-law phone)

  1. Remove original line cord.
  2. Red of the line cord to L1.
  3. White of the line cord to L2.
  4. Blue of the line cord to S.
  5. Take one wire off the bell ringer and connect  to one wire of a 3.3k resistor.
  6. Connect the other wire of the resistor to the bell terminal the wire was removed from.
  7. Insulate the green wire of the line cord.
     

French PTT Table Model U43 (Circuit diagram)

  1. Remove original line cord.
  2. Red of the line cord to 9.
  3. White of the line cord to 10.
  4. Blue of the line cord to 11.
  5. Disconnect one wire from the capacitor and insulate.
  6. The phone has no ringer in it, so a resistor does not have to be fitted.
  7. Fit a Rectifier Element across terminals 3 and 4.
  8. Insulate the green wire of the line cord.

 

French PTT Wall Model U43 (Circuit diagram)

  1. Remove original line cord.
  2. Link terminals 11 and 12.
  3. Link terminals 2 and 8.
  4. Link terminals 10 and 18.
  5. Red of the line cord to 15.
  6. White of the line cord to 14.
  7. Blue of the line cord to no where.
  8. The phone has no ringer in it, so a resistor does not have to be fitted.
  9. Fit a Rectifier Element across terminals 5 and 6.
  10. Insulate the green wire of the line cord.


 

Heemaf Type 1931 and 1952 (Circuit diagram)
This phone was made under licence from Siemens and Halske

From the information I can find the circuit diagrams are very similar in both models.

  1. Remove original line cord.
  2. Locate the capacitor.  It has two terminals.
  3. On one terminal there is a single wire - disconnect it from the terminal.
  4. On the other terminal there are two blue/white wires.  Connect the blue of the line cord to this terminal.  You need to either solder this spade connection or use thin wire and wrap the spade of the cord to the terminal.
  5. Red of the line cord to terminal A.
  6. White of line cord to terminal B.
  7. Insulate the green wire of the line cord.
  8. The phone should work, but if the ringing is not right then insert a 3.3k resistor by removing one wire from the bell coils and then soldering the resistor to that terminal and the other end to the removed wire.


Heemaf Type 1954 (Htf 2214 BPZ) (
Circuit Diagram) and 1955 (Htf 2129 BPZ4)

  1. Remove original line cord.
  2. Red of the line cord to terminal 11
  3. Remove the link between terminals 9 and 10.
  4. Insert 3.3k resistor between terminals 9 and 10.
  5. White of line cord to terminal 10.
  6. Remove the blue wire from the capacitor.
  7. On the 1955 table set terminate the blue wire from 5 above, on terminal 8 (the wire should just be long enough).
  8. On the 1954 wall set connect a piece of wire to the blue wire removed from the capacitor (see 5 above) and then run this wire to the terminal strip terminating on terminal 8.
  9. Connect blue of the line cord to terminal 8.
  10. Insulate the green wire of the line cord.

 

ITT K500 (Circuit Diagram)

  1. Remove original line cord.
  2. Remove the yellow tube wire from terminal L2.
  3. Remove the black tube wire from terminal K.
  4. Remove the red tube wire from terminal G.
  5. Remove the tube or just insulate the three unused wires above.
  6. Connect the red of line cord to terminal L1.
  7. Connect the white of line cord to terminal L2.
  8. Link terminals A and K.
  9. Blue of line cord to G.
  10. Remove the red bell wire from terminal G and connect to one side of a 3.3k resistor.
  11. Connect the other side of the 3.3k resistor to L2.
  12. Insulate the green wire of the line cord.

There is no need to fit a Rectifier Element.


Nordfern (RFT) W63a (Click here for diagram)
Due to the circuit of this phone being very basic, it will be best to convert in a manner that does not need much modification to the original.  The instruction are therefore simple, but bell tinkle may occur if other dial phones are used on the same line.

  1. Remove original line cord.
  2. Red of the line cord to terminal 4.
  3. White of the line cord to terminal 2.
  4. Insulate the green and blue wires of the line cord as they are not used.
  5. Do not fit a rectifier element as one is fitted already.

 

Siemens Halske S30054-S5137-B4-2 (Click here for diagram FG 54/5137)

  1. Remove original line cord.
  2. Red of the line cord to terminal 6.
  3. White of the line cord to terminal 14.
  4. Remove one wire from Capacitor C1 and insulate.
  5. Move the Bell green wire from terminal 6 to terminal 5.
  6. Insert a 3.3k resistor between terminals 5 and 6.
  7. Blue of the line cord to Terminal 12.
  8. Green of the line cord to terminal 13.
  9. Do not fit a rectifier element as one is fitted already.


Socotel S63 (French PTT)
click here for diagram

The terminal strips number from right to left.  The top terminals are even numbers and the terminals nearest the edge of the circuit board are odd numbers.

  1. Remove original line cord.
  2. Remove the metal link T11 / T17
  3. Connect a 3.3k resistor to T11 and T17.
  4. Red of line cord to T11.
  5. White of line cord to T13.
  6. Blue of line cord to T15.
  7. Insulate the green wire of the line cord.
  8. Try the configuration above and if the bells do not work correctly then cut one of the leads of the 760 ohm resistor.  As the resistor forms part of the anti spark quench circuit then it should really be left in situ.


Western Electric 500C & 500D

  1. Remove original line cord.
  2. Red of line cord to L1.
  3. White of line cord to L2.
  4. Blue of line cord to G.
  5. Remove the red/slate bell wire on A and connect to one side of a 3.3k resistor.
  6. Connect the other side of the resistor to K.
  7. Insulate the green wire of the line cord.
 

Western Electric 502 & 510F (May give bell tinkle on outgoing dialling)

  1. Remove original line cord.
  2. Red of line cord to L1.
  3. White of line cord to L2.
  4. Blue of line cord to RW (on the terminal strip).
  5. Connect a piece of wire between L2 (on the Network Card) and W (on the terminal strip).
  6. Remove the wires on A and K (on the Network Card) and connect them to a 3.3k resistor.
  7. Insulate the green wire of the line cord.

Onyx Telephones

Italian made telephone produced from the late 1970's.  The cases are made from flat pieces of marble, with mitred corners, glued together.  The base is metal and has a circuit board fixed to it.

These have a square circuit board inside.  There are two distinct circuit boards.  To identify which you have, locate the handset cord and see how many terminals it is connected to.  It will be three or four terminals.
The three terminal type will be labelled R, M and MR (see picture below).  The four terminal type will be labelled R, R, M and M probably with a link between the M and a R terminal, which is closest to terminal S2.

Three terminal model

  1. Remove the existing line cord.
  2. Remove any link between b and S terminals.
  3. Red of new line cord to terminal a.
  4. Connect a 3.3k resistor between terminal b and terminal S.
  5. White of new line cord to terminal b.
  6. There are two terminals S and S1 next to each other.  Blue of the new line cord connects to S.
  7. Insulate the green of the new line cord as it is not used.
  8. Cut through one of the leads of the 1uf capacitor and ensure that they do not make contact.
  9. If there are loud clicks in the earpiece, connect a Rectifier Element between the R and MR terminals.

Four terminal model

  1. Remove the existing line cord.
  2. Remove any link between terminals b and S2.
  3. Red of new line cord to terminal a.
  4. Connect a 3.3k resistor between terminals S2 and b.
  5. Link terminal B to terminal S2.
  6. White of new line cord to terminal b.
  7. Insulate the green and blue of the new line cord as it is not used.
  8. Connect a Rectifier element across terminals R and R.

 

This is the 3 terminal type and they are on the left hand side of the picture
The long yellow component to the right is the 1uf capacitor
The picture above shows the original wiring

 

 
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Last revised: October 26, 2013
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