It is not practicable to connect each subscriber directly to all the others, hence a system of exchanges has been adopted.
When a subscriber called (by turning the handle of his magneto- 'generator), the shutter of the annunciator associated with his line dropped.
Each subscriber was given the exclusive use of a circuit as in other systems, and shared a call-wire with a number of other subscribers.
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.
Then, when the connexion was made, the originating subscriber rang up the other.
At the close of a conversation the originating subscriber again entered the call-wire and requested the operator to take down the connexion.
8) a repeating coil is placed in the cord circuit, and when two subscribers are connected together the winding connected to the line of the subscriber who is talking for the time being acts as primary, and the other, which is in the line of the listening subscriber, as secondary.
Operates in the line of the listening subscriber, causing the reproduction of the speech in the latter's receiver.
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.
A circuit which serves more than one subscriber is termed a " party line."
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.
On the 1st of January 1831, without a dollar of capital, and without a single subscriber, he and his partner Isaac Knapp (1804-1843) issued the first number of the Liberator, avowing their "determination to print it as long as they could subsist on bread and water, or their hands obtain employment."
Then, having obtained particulars of the subscriber's requirement, the operator connected the second plug to the spring-jack of the wanted subscriber, whom she rang up. When.
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.
Hence this operator, when signalled in the ordinary way, can put any one of these subscribers in connexion with any subscriber whatever, without the necessity of calling upon another operator to make connexions.
The operator, whose attention is thus attracted, inserts a peg in the jack, then throws over the speaking key of the cord circuit, and having ascertained particulars of the requirement places the other peg of the pair in the nearest multiple jack of the wanted subscriber, whom she proceeds to ring up. In the meantime the callinglamp has darkened; and each subscriber's line being equipped with a cut-off relay whose function it is to disconnect tl, e calling apparatus while the circuit is in use, the insertion o r a peg is immediately followed by the disappearance of the calling signal.
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.
When a subscriber at exchange A asks for a connexion to a subscriber at B, the operator at A, to whom the request is made, passes the particulars over an order wire to an operator at B.
The latter names a disengaged junction circuit, then " tests " the line of the wanted subscriber, and if she finds it free, finally completes the connexion and rings the subscriber.
During the progress of these operations the A operator connects the originating subscriber to the junction circuit named by the B operator.
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 idea of automatic telephony is to substitute for the operator of the manual exchange an electromechanical or other switching system, which, controlled in its movement by the action of the subscriber, will automatically select, connect and disconnect circuits as desired.
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.
By means of his first selector the circuit of a calling subscriber is connected to the outgoing end of a junction whose other end terminates upon the incoming portion of a second selector in the thousand group to which the wanted subscriber belongs.
The movements of the shaft are controlled by relays and electro-magnets which operate in response to the action of the subscriber whose telephone is fitted with a 'calling mechanism which, when the subscriber calls, earths the line a certain number of times for each figure in the number of the wanted subscriber.
Another method of charge, known as the " measured service rate," is de - signed to make the subscriber pay in proportion to the quality and quantity of the service he takes.
The subscriber pays a fixed annual rent which covers a certain number of free out - ward calls, say boo; additional calls he purchases in advance in blocks of several hundred at so much per hundred, the price being reduced as the number increases.
The supervisory lamp associated with the peg in the wanted subscriber's jack glows from the time that the peg is inserted until the subscriber responds, when it darkens, in which condition it remains until the subscriber restores the receiver to the hook and causes the lamp to light up again.