Patent GB-191202672-A (GB)
Title: Improvements in Automatic and Semi-automatic Telephone Circuits.
Filed: 1912-02-01
Granted: 1913-02-03
Abstract: 2672. Siemens Bros. & Co., [Siemens & Halske Akt,-Ges.]. Feb. 1. [Addition to 2320/12.] Automatic and semi-automatic exchange systems; metering systems.-Relates to the systems described in the parent Specification in which a local call is interrupted in favour of a trunk or other preferred call by circuit changes effected by the trunk or other operator, the call relays and registers, which would usually be brought into operation when a call is commenced or ended, being prevented from acting. According to the present invention, which is particularly applicable to systems in which a pair of line relays and a differential relay are connected across the calling side of the connexion, the local call is interrupted by applying a constant potential to the speaking leads of the calling subscriber. Two methods of carrying out the invention are described, in one of which the line relay that controls the release of the connexion is provided with a second winding whereby the relay can be deenergized by the trunk operator, and in the other this line relay is brought into a kind of Wheatstone Bridge connexion by means of the differential relay under the control of the trunk operator. For the purpose of this abridgment, it will be convenient to describe, first, the method of establishing and releasing a local connexion and then the operation of the trunk operator in interrupting the call. Preliminary selector. When the subscriber T, Fig. 1, removes his receiver, his line relay R energizes the rotary magnet D, which is cut off by the relay Tr as soon as an idle group selector GW is found. The relay Tr is energized in series with a relay C1 over the contacts 3, k3, and locks up over the contacts k2, 64, 10, thus short-circuiting its highresistance winding 4 so as to mark the test lead c1 as busy. Repeater and group selector. The calling line is now connected through the differential relay X1 to the relays A1, B1, of which the relay B, remains energized throughout the connexion, and the relay A1 repeats the selecting-impulses to operate the selectors. During the movement of the impulsesender, the b-lead is continuously earthed, while the earth connexion of the a-lead is intermittently broken. The relay X1 is thus energized, and (1) maintains the relay B1 energized over a contact 11, (2) energizes over contacts 13, k4 a self-locking relay Zr, and (3) prepares the circuit of the vertical magnet H 1 at contact 17, this circuit being repeatedly closed when the relay A1 is de-energized. At the end of the first set of impulses, the relay X1 deenergizes the relay Zr, which closes at a contact 18 the circuit of the rotary magnet D1. When an idle connector is found, the relay P1 energizes in series with the relay C2, Fig. 2, and (1) shortcircuits its high-resistance winding 26 so as to mark the connector busy, (2) disconnects the rotary magnet D1, and (3) connects the leads a1, bi to the lead a2, b2. Connector. The relay C2, Fig. 2, which is energized throughout the connexion, energizes a relay V which closes contacts 29, 30, thus connecting the relays A2, B2 to the leads a2, b2 respectively. When the impulse-sender is turned to send the second set of impulses, the relay X, closes at contact 31 a circuit for the relay B2, which energizes a selflocking relay U over contacts 32, k7. The selecting- impulses are repeated by the relay A1 over contacts 37, 38, Fig. 1, 29, Fig. 2 to the relay A2, which in turn repeats them to the vertical magnet H2. At the end of these impulses, the relay X, de-energizes the relay B2, which disconnects the relay V, thus substituting the rotary magnet D2 for the vertical magnet. The final set of impulses is repeatod by the relays A1, A2 to the magnet D2, which brings the connector wipers to the contacts of the wanted line. Supply and control of ringing-current. If the required subscriber is disengaged, the relay P2 energizes in series with the cut-off relay Tr1, and (1) short-circuits its high-resistance winding 43, (2) connects the relays A2, B2 over contacts 52, 53 to the wanted line, and (3) prepares at contact 46 a circuit for the ringing-relay L. The relay V, which is de-energized after the last rotary impulse, is slow in release so that the circuit of the relay L is first closed through the right-hand winding of the relay V, thus calling the wanted line immediately. The interrupter RS interrupts this circuit for a time sufficient to de-energize the relay V, thereby connecting the relay L to the time-switch SS so as to repeat the call at intervals. During the first non-ringing interval after the called subscriber replies, the relays A2, B2 are energized, and the relay B2 closes a new circuit over contacts 47, 46 for the relay U, which cuts off the ringing-relay L. Normal release and metering of completed calls. When the calling subscriber replaces his receiver, the relay B1 closes contact 59, thus exciting a relay S which closes at contact 60 a circuit for the metering-relay Zr over contacts 61, 60, 24, lead b2, contacts 57, 62, 52, and relay A2 to the battery. The relay Zr short-circuits a resistance w2 at contact 63, thus operating the meter Z in known manner. The relay S, by closing contact 65, also short-circuits the relay P1, which by opening contact 22 deenergizes the relay C1, which in turn closes the circuit of the release magnet M. The relay S is also de-energized by the opening of contact 66, and opens the circuit of the relay Zr, which by opening contact 63 de-energizes the cut-off relay Tr, thus returning the preliminary selector to normal. The relapse of relay Ci opens at contact 68 the circuit of the relay C2, Fig. 2, which short-circuits the relay P2, so that the release magnet M2 is energized over the contacts 71, 70. If the called subscriber hangs up first, the relays A2, B2 relapse, and the relay S, Fig. 1, is energized over lead a2, and contacts 73, 55, and 72. The release then proceeds in the same way as when the relay S is energized by the calling subscriber hanging up. Release of local connexion by trunk operator. The trunk operator, having established connexion with the calling line over the trunk selector FGW and trunk connector FLW, depresses the key Ta. In the modification of the invention shown in Fig. 1, this energizes the relay X, by current passing from battery through the relays A1, Xi, lead la, and contacts l1, l2 of key Ta to ground. The relay B, now receives current from the special battery Go over the contact 11 of relay X1, and also current over the lead lb and contacts l3, l4 of the key Ta. The strengths of these currents are such that the relay B, de-energizes, and closes the circuit of the relay S which brings about the release as before, except that since the relay X1 is now energized, no circuit is closed for the metering-relay Zr so that the interrupted call is not registered. When the relay Tr de-energizes, the preliminary selector is returned to normal, but the relay R cannot be energized over the calling line a, b, as it is then short-circuited over the lead la. In the modification of the invention shown in Fig. 3, the trunk operator's key Ta connects both leads la, lb to the same potential, thus energizing the relay X1 which brings the relay B1 into a kind of Wheatstone Bridge connexion whereby the relay B1 is de-energized and brings about the release of the local call as before.