Old telephones, Candlestick and non-British phones
These telephones may be rung if you can connect a 431A line cord to the telephone.
E.G. You need to identify the line in pair of wires or terminals in the phone. This may be achieved if you use an ohmmeter, look for a high resistance reading (open circuit) with the receiver on the rest. When the receiver is lifted a low resistance reading should be obtained. Connect to these terminals the two wires of the line cord, which correspond with pins 2,5, of the BT plug. If the phone does not ring, it may have been modified, so you need to identify the ringing wire which connects to Pin 3. View examples shown below.
Note: Replacement line cords complete with BT plug can be obtained from Ebay.
Click a Phone below, for circuit and schematic diagrams - see connecting lead examples.
Candlestick phones require a different arrangement since they do not have an integral bell. Make the connections to these as above, then either plug into the spare socket another phone which has an integral bell. Or connect an old BT/GPO ac bell to a line cord using the two wires which correspond with pins 3,5, of the BT plug. (Plugs are numbered 1 to 6 starting from the plastic locking lever).
The ringing may be impaired on early British phones with 500 ohm bell coils. These phones would need to be modified. Disconnect one of the bell wires, and add a 3K3 resistor in series with these coils.
e.g. Type 700 phone, remove link and Insert a 3K3 resistor between T4-T5
For US phones pins 3,4 [red green] of the RJ11 jack correspond to pins 2,5 of the BT431A jack. An RJ11 to BT431A adapter can be provided, free on request when placing an order for a ring generator.
Caution there is a shock hazard from the ringing voltage of 120v ac.