Patent GB-191007093-A (GB)
Title: Improvements in Automatic Telephone Exchanges.
Filed: 1910-03-21
Granted: 1910-11-16
Abstract: 7093. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. March 21. Automatic exchange systems.-The testing-magnet of a selector seeking a disengaged connector is connected in a local circuit containing a resistance, and is maintained energized until its current is withdrawn when the testing-arm finds a disengaged lead. In the case of short testing-leads, the disengaged leads may be connected with the same pole of the battery as the testing-magnet, which is thus short-circuited when it reaches an idle lead. The idle leads are, however, preferably supplied with a higher battery potential than that supplied to the testing-magnet, and in this case a small current may flow in the reverse direction through the testing-magnet when this latter engages an idle lead, thereby causing the magnet to release its armature quickly. Preliminary selector. Assuming that subscriber No. 133 wishes to call subscriber No. 655, he removes his receiver, and is automatically connected by his preliminary selector VW<133> to the leads a<I>, b<I>, c<I> of an idle selector in the manner described in Specification 9634/10. First selector. The subscriber's impulse-sender is arranged to earth the b-line while the a-line is interrupted. As soon as an idle selector is found, current flows through the relays A, B, and the differential relay X to the sub-station. While the b-line is earthed, the relay X is energized and closes a local circuit through a resistance l, whereby the relays B, X both remain energized during the subsequent interruptions of the a-line, which are transmitted by the relay A to the vertical magnet of the selector. The relay X also closes at x<2> a circuit for the testing-magnet S, which remains energized until the relay X is de-energized upon the return of the impulse-sender to zero, whereupon the magnet S moves the side-switch into its second position, in which the rotary magnet is in circuit with an interrupter U. During the rotary movement of the selector, the magnet S is included in a local circuit including a resistance w<3> and contact h<1>, but when the wiper c engages an idle line, which is connected over a contact f<5> to the high-potential pole of the battery G, a feeble current flows in the reverse direction through the magnet S, which releases its armature and allows the side-switch to move into its third position. The relays A<2>, B' of the connector are thus energized by current flowing through the substation, and relay B' by closing contact b<4> brings the testing-lead c<III> into a circuit which includes the relays V, Z<1>, wiper c, contact b<4>, and resistance w<4>. The potential in the lead c<III> is such that the testing-magnet S of any other first selector testing this lead is maintained energized. The relay V is energized and opens the circuit of the release magnet R, but the relay Z<1> is not energized at this stage. Instead of using a separate relay V, the testing-magnet S could be used to control the release magnet, and would in this cise be connected to the arm h<2> in the third position of the switch. Connector. The finding of the wanted subscriber's line proceeds in a manner similar to the operation of the selector. When the earth connexion at the sub-station is removed after sending the second series of impulses, the relay X<1> closes a contact x<1> in the circuit of a relay P, which, if the desired subscriber is disengaged, is energized by current passing from the battery lead m through the winding t of the cut-off relay T<655>, contact i<1>, wiper c<2>, contact h<6>, and relay P to earth. The relay P (1) closes contact p<1> so as to send an impulse from the interrupter U through the magnet S to move the side-switch into its third position, and (2) closes a contact p<2>, thereby shortcircuiting the resistance w<4> in the circuit of the relays Y, Z<1>. The metering-relay Z' is thus energized, and short-circuits a resistance w<1> in the test lead c<I>, so as to determine the operation of the meter Z<133>, as more fully explained in Specification 9634/10. Release. When the calling subscriber hangs up his receiver, the relay B' is de-energized, and (1) closes at b<6> a circuit for the release magnet R', and (2) opens at contact b<4> the circuit of the release relay V, which in turn (1) closes the circuit of the release magnet R and (2) opens at v<5> the circuit of the test lead c<I>, so that the arms of the preliminary selector are moved round until they arrive at their normal position. The release-relay may be dispensed with, the test-magnet S then serving to control the release magnet R.