Patent GB-191001419-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: MARTIN TALBOT GRANT
Filed: 1910-01-19
Granted: 1911-01-19
Abstract: 1419. Martin, T. G. Jan. 19. Automatic exchange systems are provided with two-way trunks having a non-numerical trunking- switch and a repeater at each end of the trunk, each switch being adapted to select an idle selector under the control of the repeater at the other end of the trunk. The invention is described as applied to a system in which the switches are operated over a complete metallic line-circuit, slowrelease relays serving to make the necessary changes in the connexions during the pause between each set of selecting-impulses. In the system described, each subscribers' line terminates in an individual switch C, and a group of such switches is controlled by a master switch D, which maintains all the disengaged switches in readiness to make immediate connexion with a disengaged trunk, or first selector E, in the same general manner as is described in Specification 26,301/06. The two-way trunk 130,131, extending between two distant exchanges, is provided at each end with a repeater F, and an individual switch C<2>, similar to the subscriber's switch C, a group of such trunk switches being controlled by a master switch D<2>, which maintains all the idle trunks in readiness to make immediate connexion with a disengaged selector H. The individual switch is not shown at the end of the trunk shown in Fig. 1, but it is connected to the leads 129, 132, 133. Similarly the repeater is not shown in Fig. 2, but is connected to the leads 140, 191, 192. Subscriber's individual switch. The windings 48, 49, 50, 51 of the combined line switch and relay are wound on a single yoke, the magnetic circuit of the windings 50, 51, which control the armature 52, being independent of that of the windings 48, 49, which control the armature 53 and the plunger arm 38 of the switch. The position of all the idle plungers of a group of switches is determined at any instant by the angular position of the plunger shaft of the master switch, which, after any of the individual switches has been brought into use is actuated so as to bring all the idle plungers into a position to connect the next calling line to an idle selector. Fig. 4 shows the construction of the master switch. The selfinterrupting motor magnet 54 rotates the ratchetwheel 55, the rotary motion of which is transmitted by a suitable mechanical connexion (not shown) to the plunger shaft b so as to give this shaft a reciprocating motion to move the idle plungers to and fro in front of the bank contacts. A wiper 59 on the shaft b moves over a number of contacts a, individual to the various trunks, and serves to connect these contacts in turn to a common segment 56 connected to a relay 57, which controls a relay 58 adapted to complete the circuit of the motor-magnet 54. A sector 60 on the shaft b has a series of holes which co-operate with a pin 61 on the armature of the relay 58 so as to maintain the circuit of the magnet 54 until the plungers have been moved directly in front of a set of trunk terminals. When a calling subscriber A removes his receiver, current flows from the battery lead 100 through the winding 50, contact 89-90, line 34, sub-station apparatus, line 33, and contact 88-87 to earth. The attraction of the armature 52 closes a circuit from the battery lead 100 through the windings 51, 48 and contact 92-87 to earth. The attraction of the armature 53 disconnects the winding 50 from the line-wires, and the movement of the plunger arm 38 not only forces the springs 40, 42, 44 into contact with the terminals 41, 43, 45 of an idle selector E, but also closes contacts 94-95, and 46-47. The closing of the contact 94-95 short-circuits the winding 51, which allows the armature 52 to open the circuit of the pull-down winding 48, but before this happens a circuit is completed through the holdon winding 49, which is powerful enough to maintain the plunger arm 38 attracted, although not to pull it down initially. When the springs 40, 42 are forced into contact with the springs 41, 43, a circuit is closed from the battery lead 100, through the winding 97 of a relay 70, side-switch wiper 69, spring 40, sub-station apparatus, spring 42, and winding 96 to earth. The quick-acting relay 70 closes the circuit of a slow-release relay 78, which in turn earths the third spring 44 over a contact 106, thereby completing a circuit from the lead 100 through the hold-on winding 49, and spring 44 to earth. The grounding of the test lead 107 renders the subscriber busy to other calls. The closing of the contact 46-47, previously referred to, energizes the master-switch relay 57, which excites the relay 58, thereby closing the circuit of the motor magnet 54. The relay, 57 remains energized until the wiper 59. engages tha ungrounded contact of an idle selector, when the master switch is arrested. A precise adjustment of the switch is ensured by the locking-device 60, 61 previously described. During the movement of the master-switch, all the pull-down windings 48 are disconnected from the battery .lead at contact 93, so as to prevent the operation of any individual switch while its plunger is in motion. If a subscriber should call at this moment, he receives a signal from the busy transformer M'. Selector at first exchange. At this moment the quick-acting relay 70 is energized by current passing through the calling station, and closes the circuit of the slow-release relay 78, as previously described. When, therefore, the subscriber sends the first set of selecting impulses by interrupting the line-circuit, the relay 70 repeats them over a circuit from ground G<3>, through the contacts 98-99, 103-104, slow-release private-magnet relay 79, vertical magnet 67, and wiper 71 to the lead 100. The magnet 67 raises the wipers 64, 65, 66 to the row of terminals of trunks leading to the desired exchange. The slow-release relay 79 is energized by the first impulse and closes a circuit for the private magnet 73, which is de-energized, so as to move the side-switch into its second position, when the relay 79 is no longer energized by the selecting-impulses. In the second position of the side-switch wiper 71, the battery lead 100 is connected through a slow-acting relay 80 to the rotary magnet 68, which steps round the selector until its wipers reach the terminals of an idle trunk 130, 13 in the selected row. This hunting movement is controlled by the private magnet 73 in the usual way, the magnet 73 being de-energized when an unearthed test contact is found, so as to move the wipers 69, 69<a>, 71, 72 into the third position. In order to render the trunk 130, 131 busy to other selectors in the interval before the relays 81, 125 of the repeater F have time to respond, the test wiper 66 is earthed momentarily over the wiper 72, and contact 121-120 of the slow-release relay 80 in circuit with the rotary magnet 68. When the wipers 69, 69<a> move into their third position, the relay 70 is de-energized, but the circuit of the slow-release relay 78 (which functions also as a release relay), is maintained over the contacts 122, 121 of the relay 80 (which must consequently be quicker than the relay 78), wiper 7À2, test wiper 66, to earth at G<10>. Repeater and trunk connexions. When the wipers 69, 69<a> move into their third position, the quick-acting relay 81 is energized by current flowing through the calling station, and closes at a contact 123-124 the circuit of the slow-release relay 125, which earths at G<10> the test wiper 66 of the selector E, thus (1) maintaining a circuit for the relay 78, (2) making the trunk test busy to other selectors, and (3) by earthing the lead 129, completing a circuit through the cut-off (holding-on) winding of the plunger switch provided at this end of the trunk. The cut-off winding, corresponding to the winding 49 of the switch C, produces no movement of the plunger arm, but operates to disconnect the windings of the switch from the trunk as in the case of switch C. The relay 125 also completes the circuit of a relay 83, which connects the trunks 130, 131 to the repeater F, at the same time bridging an inductance coil 84 across the trunk. When the bridge is thus closed across the trunk, the line switch C<2>, Fig. 2, at the distance exchange operates in precisely the same manner as the switch C to extend the connexion to an idle selector H, the relays 500, 151 of which are at once energized, so that the third spring 138 is earthed over contact 137-136. Selector at second exchange. The second set of selecting-impulses sent by the calling subscriber intermittently de-energize the relay 81 of the repeater, which by opening the contact 134-135 repeats them to the selector H, which operates in exactly the same manner as the selector E. The relay 81, upon de-energizing, closes at 141 the circuit of a slow-release relay 82, which disconnects the trunk from the condensers' 144, 145, and shortcircuits the inductance 84 to prevent its interference with the operation of the switches at the other exchange. Connector. When the side-switch wipers of the selector H move into their third position, the quickacting relay 149, Fig. 3, is energized over a circuit which includes the inductance 84 at the repeater, and excites the slow-release relay 150. The third set of selecting-impulses are repeated by the relay 81, Fig. 1, to the relay 149, which in turn repeats them over a circuit from ground G<13> through the contacts 152-153, 154-155, slow-release privatemagnet relay 156, vertical magnet 157, wiper 158 to the battery lead 160. The magnet 157 raises the selector wipers to the desired horizontal row. The relay 156 is energized by the first impulse, and closes a circuit for the private magnet 163, which is de-energized so as to move the side-switch into its second position, when the relay 156 is no longer energized by the selecting-impulses. The final set of selecting-impulses are repeated by the relays 81, 149 through the relay 156 and rotary magnet 164, which