Patent GB-105272-A (GB)
Title: Improvements in Intercommunication Telephone Systems.
Inventor: DUNGEY JOHN WILLIAM
IPC: H04M9/00
Filed: 1916-04-25
Abstract: 105,272. Dungey, J. W. April 25, 1916. Intercommunication systems and apparatus.- Each station is provided with an electromagnetically-operated selector switch, the arm of which moves quickly over its contacts in a " forward " direction, when a subscriber is called, and slowly in a " backward " direction when released to select the calling-subscriber. The motion of the selector arm is arrested by an electro-magnet, which also removes a short circuit about the receiver. The number of the calling-subscriber is indicated by a lamp, the circuit of which is broken when the receiver is removed ; or the number is indicated by a pointer moving over a dial. If, in the arrangement shown in Fig. 1, a subscriber at station 1 wishes to communicate with a subscriber at station 2, he removes his receiver and places his hand selector J in contact with the line L', to which the " home " line H' of station 2 is connected. The ringing-key Q is then operated to establish the following circuit : Positive pole of battery Z, contact W, key Q, line L', home line H<1>, contacts 2, 3, and terminal a. The circuit then divides, part of the current flowing through bell D and contacts 4, 5 to negative side of battery Z, while the other part flows through the solenoid S, plunger P, armature A, and contacts 4, 5 to negative side of battery Z, The solenoid S then operates through a rack K and pinion M to move the selector to its extreme ' on ' position, the circuit of the solenoid S being- maintained at the contact of the plunger P and armature A until this position is reached, whereupon the armature A engages a stop X and the circuit of the solenoid S is broken. The selector then moves slowly back under the control of a dash-pot until it engages the contact c connected to the line L<2>, to which the home line H<2> of the calling-subscriber is connected, whereupon the magnets E at both stations are energized in series as follows : Negative side of battery B<2>, magnet E, lead l, pinion M, selector arm H, contact c, line L<2>, home line H<2>, resistance V, battery B', second magnet E, lead l<1>, contacts 1, 0 and 6, 7, hand selector J, line L', home line H<1>, resistance V, to positive side of battery B<2>. The magnet E at station 2 operates its armature 10 to engage a toothed wheel N, secured to, but insulated from, the selector arm H, thereby arresting the motion of the selector arm H at station 2 on contact c; while both magnets E operate to remove short circuits about the receivers R by opening the contacts 8, 9. The selector arm H carries an indicating-lamp L, the circuit of which is broken when the called subscriber removes his receiver. When the subscriber at station 2 removes his receiver, conversation can take place between the two subscribers, since the receivers R and transmitters T are in shunt with their respective magnets E, through which current is flowing. The selector arm H at station 2 is returned to its normal position when the subscriber at station 1 replaces his receiver, thereby breaking the circuit of the magnets E at the contacts 0, 1 of his station. The hand-selector connexion at a called station is broken at the contacts 6, 7. In the modification shown in Fig. 2, a relay RE at station 2 is energized when the ringing-switch Q at the calling- station is closed, and operates by the closure of the contacts SC, SP to place the solenoid S across the battery Z. The circuits of the relay RE and solenoid S are broken at the contacts 5, 11 and 2, 3, 4 when the subscriber at station 2 removes his receiver. In the arrangement shown in Fig. 3, one of the signal lamps LM<1>, LM<2>, LM<3>, corresponding to the calling-subscriber, is illuminated through an additional contact-arm HL, wheel N, armature 10, and contacts 4, 5, this circuit being broken when the receiver is removed. Specification 238:38/01 and 22549/14 are referred to.