|MAGNETO, RURAL PARTY LINE
LOCAL BATTERY, WITH SIMPLEX DIALLING FACILITIES
These instruments are used on magneto code ringing party lines connected to a rural automatic exchange. Up to 20 telephones per party line may be connected,
They have a dial and locking push button for exchange calling and a powerful generator for party line ringing. Provision is made in the circuit to reduce side tone to the minimum.
For ease of maintenance, the internal components of the wall set are in the form of a removable unit, while in the table set they are on the removable metal base plate.
The wall set cradle is shaped to allow the handset to be suspended vertically over the front of the instrument, to avoid releasing the connection if the user wishes to leave the telephone during a call.
External wires and cords terminate on screw connections, wiring to the wall set being direct, and to the table set via a moulded desk terminal block and cord. The internal wires are insulated with p.v.c. Cords can be p.v.c. insulated, nylon braided type if specified.
The wall set is gate-hinged on the metal back plate to allow the latter to be screwed to the wall before the telephone is fitted.
The push button on the models illustrated is not used when calling another station on the same party line, but instruments can be supplied for circuits requiring the push button to be used for all calls. Until the button is pressed, a listening circuit only is placed across the party line. Replacement of the handset releases the push button.
Black is the standard colour, but ivory telephones are also available. Cells for the transmitter battery are not supplied unless ordered.
Taken from the Ericsson catalogue, edition No. 55
Conversion to UK Plug and Socket
Not really the best phone to convert as it has a non-standard circuit and the microphone is fed by a local battery. Wiring would have to be substantially modified for the UK and partially modified for other parts of the world.
The phone could be converted to talk only, with a 1.5 volt dry battery connected to telephone terminals 9 and 10 and the exchange line on White and Red of the line cord connected to terminals 1 and 2.
Warning - do not use the hand generator or dial.
Phones with diagram N74958 could have the bell connected. Remove the orange wire from the generator and connect to one end of a 1.8uf or 2uf capacitor. Connect the other end of the capacitor to terminal 2.
A phone with diagram N81522 cannot use the dial unless serious conversion takes place. However, the phone could be converted to talk only, with a 1.5 volt dry battery connected to telephone terminals 9 and 10 and the exchange line on White and Red of the line cord connected to terminals 1 and 2. The bell may well work if the link between terminals 6 and 7 is replaced by a 1.8 uf or 2uf capacitor.
Diagram N75623 Issue 1 for Telephone N2122A20 (dated 1950)
Diagram N74958 issue 3 for Telephone N2122A21
Diagram N79981 issue 2 for Telephone N2122B20 (dated 1953)
Diagram N81522 for Telephone N2122BA2 and N2205BA (dated 1953)
Last revised: October 04, 2019