When a subscriber called (by turning the handle of his magneto- 'generator), the shutter of the annunciator associated with his line dropped.
The system of the British Post Office is worked as follows: A subscriber desiring a long-distance connexion calls up his local exchange in the ordinary way, and the operator there, being informed that a trunk connexion is desired, extends the subscriber's line to the Post Office by means of a record circuit.
The conditions permit of the circulation of the alternating currents of low periodicity, which are used for operating the bells, but in respect of the battery the circuit is open until the subscriber lifts the receiver, when the hook switch, thus released, joins the transmitter with one winding of an induction coil in series across the circuit.
The other supervisory lamp on the cord circuit is controlled in a similar manner by the subscriber who originated the call, and as that subscriber's telephone is off the hook when the peg is inserted, the lamp is not lighted at all until the subscriber replaces the receiver.
The tariff for unlimited use has to be made very high to cover the cost of the additional burdens thrown upon the service, and it only works economically to the individual subscriber who has an exceptionally large number of calls originating from his instrument.
During the progress of these operations the A operator connects the originating subscriber to the junction circuit named by the B operator.
A subscriber desiring a connexion pressed the key and communicated his own number and that of the wanted subscriber to the operator in attendance on the call-wire.
In these circumstances, when, as frequently will be the case, the person calling desires to be put in communication with a subscriber who belongs to another section, connexions must be established in the office between the two sections; this necessitates additional switchboard arrangements, and also increases the time required to put subscribers in communication with one another.
Then, when the connexion was made, the originating subscriber rang up the other.
Only calls originated by a subscriber pass through the selector switch (first selector) provided for his sole use; the calls incoming to him pass through one or other of the various connector switches upon which his circuit is multipled.