Patent GB-191401871-A (GB)
Title: Improved Circuit Arrangements for Telephone Systems.
Filed: 1914-01-23
Granted: 1915-07-01
Abstract: 1871. Siemens & Halske Akt.-Ges. Jan. 25, 1913, [Convention date]. [Addition to 28,751/12.] Automatic and semi-automatic exchange systems.- Systems of the kind described in the parent Specification, in which some subscribers are equipped with number-senders while the connexions required by other subscribers have to be set up by operators, are modified so that the connexions of both classes of subscribers are made through the same non- numerical switches, thus simplifying the changes necessitated when a subscriber is transferred from one class to the other. In some cases, each subscriber has an individual preliminary selector, and there is a second series of preliminary selectors common to both classes. If call-finders are employed, both the first and second series of non- numerical switches may be common to the two classes of subscriber, as is also the case when subscribers of both classes are connected to the same party-lines. In every instance, an operator is automatically connected over a lateral circuit when the call is from a subscriber of the semi-automatic class. In the arrangement shown in Fig. 5, the first and second preliminary selectors VW1, VW<1>I, VWII are at a district office which is connected to the main exchange by two-wire junction lines VL. In the case of a call from a semi-automatic subscriber H, a relay F, energized over the fourth wipers of the switches VWI, VWII, grounds the b side of the junction line so as to energize a relay B, which closes the circuit of the operating-magnet D of the service selector DW. The operator selected by the switch DW enquires the wanted number, energizes the relay T3 to disconnect the calling line, and sends the requisite sets of impulses to establish the wanted connexion. The relays T2, T3 are then de-energized by the opening of contacts I, II, and the switch DW restores itself to normal. In the case of a call from a full-automatic subscriber V, the impulses sent by the subscriber are repeated by a relay R over the a side of the junction line to a relay A of the group selector GW. The relay F is not energized, the wiper d<1> of the subscriber V being disconnected from battery, and the service selector DW is, consequently, not set in action. Instead of operating the discriminating- relay F over additional wipers of the non-numerical switches, reverse batteries may be employed which control it over'the test lead c. In the arrangement shown in Fig. 3, an automatic subscriber V and semi-automatic subscriber H are connected to the same party-line. When either subscriber calls, he is connected by the switches VWI, VWII, to a group selector GW, and the relays A, B are energized. The subscriber V then establishes the wanted connexion in the usual way, but the subscriber H presses a key 18 which de-energizss the relay B while keeping the relay A energized. This completes the starting-circuit of the magnet D, which moves the switch DW out of its normal position and thereby opens its own circuit at the normal contact 21. When the key 18 is released, the relay B energizes again and completes a fresh circuit for the magnet D over the off-normal contact 31, and the switch DW moves on until it finds an idle operator. In a modification, shown in Fig. 4, the key 18 at the semi-automatic sub-station is dispensed with, its function being performed by the switch hook 33. When the subscriber lifts his receiver, the switch hook 33 rises to a middle position in which it is held by a detent 48, the magnet of which is, in this position, connected by a contact 50 to the line b. The preliminary selector individual to the line a, b is started by the momentary grounding of the line a at a contact 32. When the line has been connected by first and second preliminary selectors to a group selector, the detent magnet 49 is energized in series with a relay at the selector. The switch hook 33 rises to its final position, and the relay closes a starting- circuit for the service selector, which selects an idle operator.