Patent GB-191001420-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: KEITH ALEXANDER ELSWORTH
Filed: 1910-01-19
Granted: 1911-01-19
Abstract: 1420. Keith, A. E. Jan.19. Automatic and semi-automatic exchange systems are provided with means for manually supervising and controlling the line switches, selectors, and connectors, without the necessity of directly inspecting such apparatus. The trunks leading to the selectors and connectors are connected to individual jacks at the exchange attendant's switchboard, and the attendant's apparatus comprises means whereby he may (1) release any off-normal switch, which failed to release properly in normal working, (2) trace the selectors and connector used in making any particular connexion, so that the cause of failure may be readily determined, and (3) connect himself to any subscriber's line, even if that subscriber is busy, by operating one of the ordinary connectors serving that line, with the object of communicating with that subscriber or of testing his line for faults &c. The invention is particularly applicable to districtoffice systems, in which the line switches and connectors of a group of stations are located at sub-centrals, from which trunks run to the main exchange, at which the first and second selectors are located. The system in connexion with which the invention is described will first be explained, and the characteristic features of the invention will be more fully explained in the last three paragraphs of the abridgment. Sub-station apparatus. The impulse-sender is so constructed that a preliminary impulse of comparatively long duration is sent over the rotary lead prior to each set of selecting-impulses sent over the vertical lead, these being followed as usual by a single impulse over the rotary lead. The vertical impulse-spring 23, Fig. 6, has a lug 248 which is engaged by the teeth of the impulse dial and presses the spring 23 against the ground spring 20. The rotary impulse-spring 24 has on its under side a V-shaped member 249, which co-operates with an auxiliary spring 250 having the lower part 251 curved outwardly. During the outward movement of impulse dial, the rotary tooth passes on to the spring 250 and causes the spring 24 to engage the ground spring 20 for a comparatively long time, but during the return movement, it passes under the spring 250 and engages the member 249, closing the contact 20-24 for a short time only. Subscriber's individual switch. The subscribers' line switches C, C', Figs. 1 and 2, and the master switch D resemble in their action and construction the corresponding switches described in Specification 26,301/06. When the subscriber removes his receiver and proceeds to rotate the dial of his impulse-sender, a preliminary impulse of considerable duration passes through his trip-magnet 47 and over his rotary line 32 to earth at G, thus operating his line switch, which extends connexion to an idle trunk 90, 91 by closing contacts 63-64, 65-66. The closing of a contact 67-68 earths the subscriber's test lead 95 and also energizes a cut-off relay 46. The closing of a contact 69-70 completes a circuit from the battery lead 160 through the release magnet 48, to the contact 69-70, where the current divides, part passing over the high-resistance release relay 166, trunk 91, side-switch arm 104, and a relay 122 to earth, the other part passing to the contact 84, individual to the trunk 90, 91, contact arm 75, segment 74, relay 159, and lower winding of a relay 73 to earth. The release magnet 48 is not energized by this current, owing to the resistance of the relays 122, 73. The energizing of the relay 122 (1) completes a temporary circuit through a lamp 39, common to a group of first selectors, this circuit being afterwards interrupted when the side-switch arm 104 moves into its third position, and (2) connects a busy generator I to the trunk 90 and the upper contact of a jack 40, bridged across the trunk 90, 91. The energizing of the relay 75 completes the circuit of the self-interrupting motor magnet 71, which rotates the masterswitch shaft 60 until the arm 75 engages an unearthed contact, belonging to an idle trunk. The plungers of all the other line-switches are thus brought into position to make connexion with an idle trunk. First selector. The first set of selecting-impulses sent over the vertical lead 31 to the vertical relay 108 are repeated to the vertical magnet 96 over a contact of the private magnet 99. The succeeding rotary impulse is repeated by the relay 109 to the private magnet 99, whereby the side-switch is moved into its second position, in which the rotary magnet 97 is intermittently energized. The hunting action for an idle second selector is controlled in the usual way by the magnets 97, 99, the side-switch being moved into its third position when an unearthed contact is found by the wiper 121. The arm 104 thus opens the circuit of the lamp 39, but the arm 103 completes a circuit through the back-release relay 115 and wiper 121 for a supervisory relay 180 of the second selector. Second selector. The relay 180 (1) closes a temporary circuit through a lamp 41, common to a group of selectors, this circuit being interrupted when the side-switch moves into its third position, and (2) connects a busy generator J to the trunk 175 and jack 232 individual to the trunk 175, 176. The operation of the second selector proceeds in the same way as the first selector, the only difference between the two selectors being that the springs 123, 124 are connected to the test lead instead of being earthed, and that a special resistance 255 is provided for the purpose of releasing the connexion by the exchange attendant, as described later. Connector. In the third position of the sideswitch arm 244, Fig 1, a circuit is closed from ground G<11> through the back-release relay 213, test lead 194, and through the relays 142, 145, Fig. 2. The relay 142 opens a contact 260-261 and thus prevents the glowing of the lamp 132<a> when the contact 141<a> is closed on the first vertical movement of the connector. The relay 145 (1) closes a temporary circuit through the group lamp 42, which is interrupted when the side-switch arm 39 moves into its third position, in which, however, a circuit is closed through a group lamp 43 as long as the test lead 194 is earthed at the second selector, and (2) connects the busy generator K to the trunk 192 and jack 225. The glowing of the lamp 43 indicates to the attendant that a connector in this group has been put into connexion with some line. The third set of selecting-impulses are repeated by the relay 128 to the vertical magnet 130, and the succeeding rotary impulse is repeated by the rotary relay 129 to the private magnet 133, which moves the side-switch into its second position. The final set of selecting-impulses is repeated by the relay 128 to the rotary magnet 131, and the succeeding rotary impulse energizes the private magnet 133 as usual. Busy test and busy release. If the called line is busy, its test-lead will be earthed over the contact 240-241 at its line-switch, or through the contact 269-268 and side-switch arm 137 of some other connector. In either case, the private magnet 133 of a calling connector, when energized by the rotary impulse succeeding the final set of selecting-impulses, completes a release circuit from the battery lead 160 through the release magnet 134, contact 242-243 of the private magnet, sideswitch arm 137, contacts 268-269, and the earthed test lead 203. The connector is thus released, and the relay 145 is again energized. The calling subscriber is notified that the desired connexion cannot be obtained by a current from the busy generator K. The selectors E, F and the line switch C are released when the calling subscriber replaces his receiver. Supply of ringing-current. If the required line is disengaged, the side-switch passes into its third position, and the calling subscriber rings up the required station by depressing his calling button 37, thus earthing the vertical relay 128, which completes the circuit of the ringing-relay 132, thus bridging the generator L across the called line. Release. When the calling subscriber replaces his receiver, both sides of his line are simultaneously earthed; and the relays 128, 129 complete the known release circuit through the release magnet 134 and the back-release relay 213 of the selector F, which completes a circuit through the release magnet 215 and the release relay 115 of the selector E. The release relay 166 controlling the release of the line switch C is energized when the rotary lead 32 is earthed, and completes a circuit for the release magnet 48 through the contact 218- 219, 64-63, and vertical line 31 to earth at the substation. Release of off-normal switches by attendant. If, for any reason, all the switches are restored to normal except the second selector F, for example, the wipers 189, 190, 191 will remain in connexion with the trunk 192, 193, 194, and the side-switch arm 244 will remain in its third position. The relay 145 is thus energized and lights the group lamp 42, at the same time connecting the busy generator K to the individual jack 225. The continued glowing of the lamp 42 indicates to the attendant that some connector trunk has been seized and that the connector remains in an idle position. To determine which trunk is thus occupied, the attendant moves key b to close contact 220-221, and key c to close contact 222- 223, and proceeds to test the group of jacks a<2> with the plug n until the busy-signal from the generator k is heard in the receiver 226. To release the off-normal selector, the attendant restores the key b, reverses the key c, and fully inserts the plug n in the jack o, thus grounding both trunks 192, 193 simultaneously, whereby the line relays 128, 129 are both energized and the circuit of the release relay 213 of the selector F is again closed. The relay 213 closes a local circuit including the resistance 255 for the release magnet 215. Similarly, if the line switch C or the first