Patent GB-191310864-A (GB)
Title: Telephone Exchange System.
Inventor: JOHNSON MORTON LEWIS
Filed: 1913-05-08
Granted: 1914-05-07
Abstract: 10,864. Johnson, M. L. May 8. Semi-automatic exchange systems. - In a system in which an operator connects both the calling and called subscribers to a link circuit by numerical selectors, hunting switches are used to find an idle link circuit. In the system described, a calling line is connected by a preselector to an idle operator, who enquires the numbers of the calling and wanted subscribers, and then plugs into a pair of jacks, designated as idle by a visual signal, which lead to a non-numerical switch adapted to connect the operator to an idle link circuit. The link circuits terminate at each end in group selectors, through which connexion is established with the calling and called subscribers respectively. When the connexion is completed, the operator's apparatus is disconnected, and the calling subscriber's pre-selector is restored to normal, the release of the connexion being under the control of the subscribers. The operations in further detail are described below. Connexion of calling line to idle operator. When a subscriber 882, Fig. 5, removes his receiver, his line relay 31 completes a circuit through a sluggish interrupter relay 33 for the rotary magnet 34, which rotates the wipers 36, 37, 38, until the test wiper 37 finds an idle operator's circuit, whereupon the private magnet 39 is de-energized, moving the side-switch arms 35, 40, 41, 42 into their second position, in which the rotary magnet is cut off by the arm 35, the test wire 43 grounded by arm 41, and the calling line 10, 11 connected to the operator's circuit 13 over arms 40, 42. Two circuits 13 for each operator are shown, the operator having keys 47, Fig. 2, whereby she can connect her speaking set 48 to the calling line, in response to the lighting of a call lamp 45, controlled by a relay 46 in circuit with the test wire 43. Selection of idle link circuit. Having ascertained the number of the calling and wanted lines, the operator inserts a pair of plugs 18, 18<1>, associated with impulse-transmitters 14, 15, into a pair of jacks 17, 17<1> wired to a hunting-switch 16, Fig. 2. The pairs of jacks are multipled in front of the different operators, jacks connected to idle hunting-switches being indicated by visual signals 47'. The insertion of the plug 18 energizes a relay 56, thus completing a circuit through a sluggish interrupter relay 59 for the rotary magnet 60, which rotates the wipers 62 ... 67 until the test wiper 64 finds an idle link circuit, whereupon the private magnet 68 is de-energized, moving the side-switch arms 61, 69, 70 into their second position, in which the arm 61 cuts out the rotary magnet and energizes a relay 71. The impulse-transmitter 14 is then connected over the jack 17, wipers 62, 63, leads 77, 73 to the line relay 76 of the group selector 20, Fig. 3, which is used to connect the link circuit 19, Fig. 3, to the calling line. Similarly the impulse-transmitter 15, Fig. 2, is connected over the wipers 66, 67 and leads 77', 73<1> to the line relay 76<1> of the group selector 21, Fig. 3, used to select the wanted line. The relays 76, 76<1> energize slow-release relays 79, which earth the lead 80 so as to mark the link circuit as engaged. Operation of group selectors 20, 21, Fig. 3. These are operated in the manner described in Specification 15,133/11, except that the rotary magnet 88, instead of interrupting its own circuit, is in series with a self-interrupting relay 89. When the side-switches 83<1>, 84, 85 move into their third positions, the switching- relays 75 are energized and extend the leads 73, 77 and 73<1>, 77<1>, to the line relays 90, Fig. 4, of the connectors. Operation of connectors 22, 23, Fig. 4. The connector 23 for selecting the wanted subscriber operates in the manner described in Specification 15,133/11 as regards the selection of the desired line, and the application of ringing-current. It is, however, provided with an additional test wiper 98 and relay 117, which prevent connexion from being made with a subscriber who has called the operator but whose connexion has not been completed. Prior to the completion of the connexion, the calling subscriber's line relay 31, Fig. 5, grounds a special test lead connected to contacts in the path of the extra wiper 98. The connector 22, Fig. 4, for selecting the calling subscriber resembles the connector 23, but contains no ringing or testing mechanism. A switching - relay 110, energized when the side-switch passes to third position, extends the connexion to wipers 95, 97, and opens a contact in the circuit of the release magnet 108. After the disconnexion of the line and slow-release relays 90, 91, the relay 110 is kept energized over wires 92, 80, Fig. 3, and the armature of the slow-release relay 91 of the connector 23. Disconnexion of operator's apparatus, and of calling subscriber's pre-selector, and completion of through connexion. The wipers 96 of both connectors 22, 23 complete circuits for the cutoff relays 24, Fig. 5, of the calling and called subscribers, thus disconnecting the line relays 31, and thereby energizing the release magnet 120 of the calling subscriber's pre-selector, and preventing the operation of the called subscriber's pre-selector when he replies. When all the selecting-impulses have been transmitted by the operator, she depresses a release key 50, Fig. 2, which energizes a self-locking relay 49. thereby opening at its armature 55 the circuit of the relay 56, which in turn energizes the release magnet of the idle-link-circuit-selector 16. The release of the selector 16 de-energizes a relay 124, Fig. 3, which energizes the relays 74 of both selectors 20, 21, thereby connecting both the calling and called lines to the link circuit 19. Microphone current is supplied to the calling subscriber through the windings of the relay 90 of the connector 23, and the wipers of selectors 21, 20 and connector 22. Release. The release relay 91 of the connector 23 is controlled by the relay 90 and also by the back-bridge relay 114, so that when both subscribers hang up the relay 91 energizes the release magnet 108 of connector 23, and removes the holding ground from the leads 92, 80, whereby the switching-relays 75 of the selectors 21, 20 and the similar relay 110 of the connector 22 are all de-energized. The relays 75, 110 complete the circuits of the release magnets 93, 108.