Patent GB-191001423-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: DICKER STANLEY GORDON SINCLAIR
Filed: 1910-01-19
Granted: 1911-04-19
Abstract: 1423. Dicker, S. G. S., [Automatic Electric Co.]. Jan. 19. Automatic exchange systems, in which provision is made for party line working. The selecting and connecting operations are controlled over the two sides of the calling line in series, there being no operating grounds at the substations, and ringing current of the right frequency to affect the desired subscriber is selected by a step-by-step switch associated with the connector. Reverting calls can be made through the usual connectors or through special ring-back arrangements associated with a particular division of the selector bank contacts. To complete such calls it is necessary to depress a ringing-button which cuts a resistance out of line, this operation being unnecessary in the case of lineto-line connexions. Calls intended for a party line subscriber who has been permanently disconnected are received by a device at the exchange which responds to the particular frequency of current and signals an attendant. The constructions of selecting and connecting switch employed are those described in Specification 26,301/06. The operations when subscriber A, Fig. 1, calls subscriber A<4>, Fig. 2 (No. 22,201), both being on party lines, are as follows. Preliminary selector or line switch C, Fig. 1. When subscriber A removes his receiver from the hook a circuit is closed from ground G<1> over both sides of the line through the individual line-relay 23, to battery lead 78, energizing a magnet 22 which depresses the line terminals 25, 27, 29, 31 on to the trunk terminals of an idle first selector E. The mechanism associated for this purpose with the magnet 22 is controlled in a manner described in Specification 1419/10, by a master switch D, which serves a group of lines and connects a calling line on to an idle first selector without the delay imposed by a hunting movement. First selector E, Fig. 1. A relay 51, with two coils connected to the two sides of the line, is energized as soon as the selector is seized and closes the circuit of a sluggish release relay 52, which remains alive until release is affected. The relay 52 connects a test-lead 95 to ground G' and a branch from this circuit is taken through the cut-off relay 24 and magnet 22 of the preliminary selector C, so as to lock the magnet 22, the first circuit of which has been opened by the action of its own armature on the springs of relay 24. Two carrent interruptions representing the first digit (2) are now transmitted by the toothed wheel 8 opening springs 9, 10, and are forwarded as impulses by the relay 51 to the vertical magnet 44, which steps up the wipers 41, 43, 42 to the second level. The sluggish private magnet relay 54, connected in series with the vertical magnet 44, is energized by the first of these impulses and becomes de-energized after the last of them, and the private magnet 50 controlled by the relay 54 moves the side switch in the usual manner to its second position. This cuts out the vertical magnet 44 and cuts in the rotary magnet 45 which automatically steps round the wipers until an idle second selector is found, and then moves the side switch into its third position, extending the line connexions as indicated in thick lines to the second selector F. Second selector F, Fig. 1. The line relay 104 and release relay 105 are energized as described in connexion with the first selector and a test circuit is closed from ground G<8> to all the test bank contacts 109 special to the selector F. A branch from this circuit extends through the test wiper 43 and side-switch arm 49 and locks up the release relay 52 of the first selector before the cutting out of the line relay 51 has bad time to de-energize it. A sluggish relay 55 controls this circuit, and up to the moment of its de-energization, closes a circuit from ground G<7> through the side switch arm 49 and test wiper 43 to the test contacts 109. so that the selector F cannot be seized by another first selector in the interval before the relay 105 energizes. The operations by which the second digit extends the line-connexions to a connector of the desired "thousands" group are the same as described in connexion with the first selector. Connector H, Fig. 2. Line relays 60, 61 are energized as soon as the connector is seized and the circuit of the sluggish release relay 118 is closed from grounds G<9>, G<10> through springs 116, 117 of a back-bridge relay 58. A test circuit is thus completed from ground G<9> through side-switch arm 119 to test lead 122, and a locking circuit is extended from this through test-wiper 125, Fig. 1, and side-switch arm 126 to the release magnet 105 of the second selector, and a further branch through side-switch arm 106 and wiper 43 continues the locking-up of the first selector release magnet 52. The current interruptions representing the third digit (2) are translated into impulses by the line relay 60 and forwarded from ground G<10> to vertical magnet 130, which raises the wipers 158, 143, 159 to the second level. Then, as described for the first selector, the private magnet relay 133, in series with the vertical magnet 130, de-energizes, and the private magnet 135 which it controls moves the side switch into its second position. The relay 133, while energized, shortcircuits relay 61 by grounding spring 136, and so decreases the resistance in the circuit of relay 60. The impulses representing the last digit are forwarded from ground G<10> through private magnet relay 133 and rotary magnet 138, which is cut in by the side-switch in its second position, and the wipers 158, 143, 159 are moved on to the bank contacts of the party line 169, 171. Busy test. If this line is busy, the side-switch does not move into its third position when the private magnet relay 133 de-energizes, because the private magnet 135 is kept alive by a circuit from the grounded test-contact, test wiper 143, sideswitch arm 147, springs 148 and 149 and coil of relay 142. lower springs of relay 133, through private magnet 135 to battery lead 78. The relay 142 at once breaks this circuit by opening springs 148, 149 but closes a self-holding circuit from ground G<9>, through side switch arm 119, upper springs of release relay 118, springs 150, 149 of relay 142, and through relay 142 and private magnet 135 to battery lead 78. A busy signal is now sent back from battery lead 78, through secondary coil of busy signal M, springs of private magnet 135, side-switch arm 153, lower springs of relay 59, condenser 156 and line 124 to the calling substation, returning over line 123 and through relay 60 to battery lead 78. The calling subscriber then hangs up his receiver to release the instruments. The rotary magnet 138 is cut out by relay 142 to prevent further rotary motion in case the busy signal should be disregarded and the last digit dispatched. Disconnexion of preliminary selector of called line. If the called line is idle, the side switch moves into its third position as soon as the relay 133 and private magnet 135 de-energize, and the connections are extended as indicated in thick lines to the party line 169, 171. The side-switch arm 147 in its third position closes a circuit from ground G<11> to test-wiper 143, making all the test contacts of the called line busy, and a branch circuit energizes relay 160 and magnet 162 so as to cut out the preliminary selector of the called line by opening the springs of relay 160. The current is not sufficient to energize magnet 162. Supply of ringing and talking current to party line. The last digit (1) is forwarded by relay 60 as a current impulse from ground G<10> over circuits previously traced to private magnet relay 133, magnet 65, side-switch arm 134 to battery lead 78. A ratchet-wheel 64, controlled by magnet 65, rotates a pair of wipers on to the terminals of the first of a series of ringing generators L, L', L<2>, L<3>, and, as soon as the sluggish relay 133 deenergizes, the ringing relay 59 is intermittently energized over a circuit from ground G<12>, through interrupter 163, springs of relay 58, relay 59, upper springs of relay 133, through a pair of springs closed by the first movement of ratchetwheel 64 and through side switch 134 to battery lead 78. At each response of the ringing relay 59, the called line is disconnected from the calling line and connected to the ringing generator L. The current thus supplied to the party line 169, 171 is of such frequency as to actuate only the ringer of subscriber A<4>, who takes down his receiver and completes the talking circuits, current being supplied to the called line through the two windings of the back-bridge relay 58, which are connected respectively to ground G<11> and battery lead 78. The relay 58, as soon as energized, cuts out the ringing relay 59. Release. When conversation is finished, the calling subscriber restores the instruments by hanging up his receiver, so as to break the line circuit and de-energize the connector line relays 60, 61, and, consequently, the release relay 118. This closes a circuit from ground G<10>, through springs of relay 60, lower springs of release relay 118, release magnet 67, and contact 176 (closed at first movement of the connector) to battery lead 78. The release magnet 67 restores all the connector apparatus (including the ringing selector 64) and the de-energization of relay 118 opens the previously-traced locking-circuits of the corresponding relays 105 and 52 of the selectors F, E, and of the magnet 22 of the pre-selector C, and these instruments are restored in a similar manner. Signalling exchange attendant when it is attempted to ring up a permanently disconnected party-line subscriber. A set of apparatus shown at O, Fig. 2, and comprising a harmonic relay 70, responsive to current of the frequency special to the disconnected subscriber, is connected at the exchange to the party line 169, 171 to which the subscriber had belonged. When the relay 70 is operated by a cal