Patent GB-191218498-A (GB)
Title: Improved Circuit Arrangements for Automatic Telephone Systems.
Filed: 1912-08-12
Granted: 1913-09-12
Abstract: 18,498. Siemens & Halske Akt.-Ges. Aug. 14, 1911, [Convention date]. Automatic and semi-automatic exchange systems.-In automatic systems in which local or other calls are interrupted in favour of trunk or other preferred calls, instead of providing additional connectors for making the trunk connexions, the same connectors are used for both local and trunk calls. The necessary changes in the connexions of the connectors are brought about either by a particular combination of current impulses, such as would be obtained by prolonging the last impulse in the last digit of the wanted line, or, in the case where the junction leads from the trunk operator's position lead directly to the connectors, hv means of an additional relay inserted in the test lead of the incoming junction. As a result of these changes in the connexions, the usual test and ringing relays are not brought into action. To each group of ten connectors are allotted one or more sets of trunking-apparatus including special testing-arrangements, whereby the trunk operator is informed whether the wanted line is free, is engaged in a local call, or in a trunk call. When a connector is seized for a trunk call, one of these sets of apparatus is automatically associated with the seized connector, the contact arms forming the incoming and outgoing ends of the set being connected respectively with the leads to, and the contact wipers of, the connector. This set of apparatus remains associated with the connector as long as the trunk connexion lasts, the talking circuit passing through the contacts of the set. The method of operating the connector LW to establish a local call is as follows:--When the connector is seized by a group selector, such as is described in Specification 2672/12, the relay C is energized, and closes a contact 3 so as to connect the battery to the vertical and rotary magnets H, D, and relays A, V. The relay V is energized over a contact i, opened on the first rotary movement of the connector, and by attracting its armatures 6, 7 prepares circuits for the ringing and testing relays L, P, and by means of its armatures 4, 5 connects the relays A, B to the leads a, b. When the calling subscriber operates his impulse-sender, the relay B is continuously energized over the lead b, and closes at its contact 10 a circuit for a relay U over a normal contact k2. The relay U locks up over its contact 16, and prepares at contact 14 the circuit of the vertical magnet H which is actuated when the relay A, energized over the lead a, intermittently closes contact 15. At the end of the ' tens ' impulses, the relay B opens at contact 10 the circuit of the relay U, which is not energized when the relay B is again energized during the transmission of the ' units ' impulses, because of the opening of contact k2. The last set of impulses is consequently repeated by the relay A to the rotary magnet D. Normal busv test. The slow-release relay V, which is energized by the relay B during the rotary movement of the connector, prepares at its contact 7 a circuit for the test relay P which is closed over contacts 11, 17 when the relays A, B de-energize. If the wanted line is engaged, the relay P is not energized, and as soon as the relay V de-energizes the lead a to the group selector is earthed over contacts 5, 25, 1, 18, k1, and brings about the release of the connexion. Ringing-current, supply and control of. If the wanted line is idle, the relay P is energized, and (1) short-circuits its high-resistance winding p6 over contacts 18, k1 so as to mark the line engaged, and (2) energizes the ringing- relay L over contacts 21, 9, 22 and at first over the winding 2 of the relay V and an interrupter Ub. The relay L is thus at once energized and connects the ringing-generator to line over its contacts 23, 24. When the interrupter Ub is open, the relay V de-energizes so that the circuit of the ringing-relay L is next closed over the slowly-moving interrupter SS, which repeats the call at intervals. When the called subscriber replies, current flows over the contact 3, relay A, contacts 20, 24, called line, contacts 23, 19, and relay B to ground. The relay B, by attracting its armature 9, disconnects the ringing-relay L, and again energizes the relay U, which completes the talking circuit by attracting its armatures 12, 13. Trunk calls. Two methods of operating the connector LW to obtain a connexion for a trunk call are described, and in that shown in Fig. 1, the trunk operator is assumed to have obtained control of the connector LW through a group selector such as is described in Specification 19,231/11. The connector wipers are brought to the contacts of the wanted line in the same way as for a local call, but the last impulse over the a-line for the units digit is prolonged, whereby the relay A is kept, energized after the relay B has de-energized. The simultaneous closure of the contacts 8, 26, which does not occur during the establishment of a local call, closes a circuit from the battery over the contact 3, winding 1 of relay A, contacts 8, 26, for a relay An which serves to associate an idle set of trunking-apparatus AS1 with the connector LW. The relay A remains energized over this circuit and prevents the testing and ringing relays P L from becoming operative. In the second system described in which the connectors are directly accessible from the trunk operator's position, a relay in the incoming test lead of the connector closes a contact which replaces the contacts 8, 26 in circuit with the relay An, The two systems are otherwise substantially identical. Connexion of special trunking-apparatus with connector. Each set of trunking-apparatus AS1, AS2 comprises an auxiliary selector ZW1, ZW2, which connects it to the seized connector LW, special test relays P1, P2 which control the connexion of the tone signalling-devices Fr, FW, OV, for showing if the line is free or how it is engaged, a bridge relay S for supplying current to the called line, and a repeater Ue in the speaking-circuit. When the relay An is energized, the relays R1, R2 of all the idle auxiliary selectors are energized, but only the first relay R1 remains energized, and closes at a contact 30 a circuit for the rotarv magnet D1, which rotates the wipers o4, o5, o6, o7, o8, o9 until the wiper o6 finds the lead 27 of the connector LW. The relay P3 is then energized, and (1) cuts off at 31 the rotary magnet D1, (2) short-circuits its high-resistance winding so as to prevent any other auxiliary selector connecting to the connector LW, (3) de-energizes the relay An by shunting it with its low-resistance winding, and (4) de-energizes the relay R1, which restores the circuit of the relay R2 so that the trunking-apparatus AS, is brought into use for the next trunk call if the apparatus AS1 has not been set free meanwhile. When the wipers o4, o5, o6 make connexion with the trunk a, b, c, the wipers o7, o8, o9 connect to the wipers o1, o2, o3 of the same connector. Test of local line by trunk operator. The relay A1 is connected over contacts 43, 41, o4 to the selector trunk a so that it is energized when the trunk operator earths the a-lead by depressing her testing-key. The relay A1 closes contact 44, thus preparing a circuit for the buzzers Fr, OV, FW, which will he established over the windings 70, 71 of the relays A1, B1 when one of the contacts 37, 45, 46 is closed; the relay A1 also closes contacts 49, 50, which connect the battery through a resistance w<3> to the left-hand winding of a relay P1, which had been previously energized over its righthand winding by the relay R1 over contact 35, and had locked up over contacts 36, 35. If the wanted subscriber is disengaged, or is engaged in a local connexion, the currents over the windings p1, p2 neutralize each other, so that the relay V1 is energized over contacts 38, 49, 35, locks up over contact 51, and earths the relay P., at contact 52. If the wanted line is disengaged, the relay P2 is energized over wipers o9, o3, and (1) by closing contact 46 connects the disengaged tone signal Fr to the trunk operator, (2) by closing contacts 54, 55 bridges the relay S and battery across the called line, and completes the connexion to the leads a, b through the repeater Ue, and (3) by closing contact 35 short - circuits its highresistance winding so as to make the called line busy to other calls, both local and trunk. The release of the relay V1 brings about the application of ringing-current to the called line in a manner similar to that shown for the connector LW. When the subscriber replies, the relay S is energized, and cuts off the relays A1, B1 from the trunk a, b, thus controlling a clearing relay at the trunk operator's position. If the wanted line is engaged in a local call, the relay P, is de-energized and the relay V1 energized as before, but the relay P2 does not energize, so that the tone signal OV is connected to the trunk operator. If the wanted line is engaged in a trunk call, its test lead is earthed through the low-resistance coil p<3> of a relay such as P2, so that the current flowing through the left-hand winding of relay P1 cannot neutralize the other winding. The relay P1 remains energized and connects the tone signal FW to the trunk operation. Release of local connexion. If the wanted subscriber is engaged in a local call, the relay P2 is not energized and consequently the relay V1 remains locked up after the relay P1 relapses. When the trunk operator releases her testing key, the relay A1 de-energizes and by closing contacts 47, 48 connects ground and a special battery 63 over the contacts 59, 60 of relay V1 to the speaking leads of the called subscriber. If the wanted subscriber is the calling subscriber in the local connexion, a line relay at the gronp selector is thus energized and releases the local call as described in Specification 2672/12. If the wanted subscriber is the called subscriber in