Patent GB-191117211-A (GB)
Title: Improvement in Semi-automatic Telephone Exchange Systems.
Inventor: MCBERTY FRANK ROBERT
Filed: 1911-07-27
Granted: 1912-07-25
Abstract: 17,211. McBerty, F. R. July 27, 1910, [Convention date]. Automatic and semi-automatic exchange systems.-A system is described in which a centralstation operator answers a calling subscriber in the usual way, by plugging into his line-jack, and then extends the connexion to the line of the wanted subscriber through automatic selectors controlled by a key-set on which she writes down the wanted number. The claims relate to the following features. (1) Each cordcircuit is provided with separate supervisory lamps, while that part of an operator's equipment which is common to all the cord-circuits, for instance the listening-set and master-keys controlling release &c., is automatically associated with any cord-circuit that is put into use. (2) The connective circuits are controlled by sequence switches, which can be restored by the operator at any stage by means of a master wipe-out key. (3) The lamps for supervising the calling and called subscribers serve also tn indicate the progress of the switching and restoring operations. (4) The restoration of the selectors normally follows when the operator withdraws the answering-plug, but this may be prevented by the operator first pressing her listening-in key. Other features of the system herein described, some of them applicable to manual and to full-automatic systems, form the subject-matter of divided applications 8571/12, 8572/12, and 8573/12. Construction of selectors, cord-finder, and sequence switches. The selector shown in Fig. 1 is practically identical with that described in Specification 16,867/11. Specification 20,841/09 is also referred to in this connexion. The cordfinder shown in Fig. 3 is a one-coordinate hunting-switch comprising a set of five brushes 309 &c. mounted on a rotatable carriage, which is set in motion by a clutch magnet 323 and stopped by a holding-magnet 324 in the same way as the brush-carriage of the selector. The cord-finder has no normal position but remains in the position in which it was last of service. The sequence switches employed to control the succession of operations in the different trunkcircuits are described in Specification 20,840/09. This description is repeated in the present Specification as open to inspection under Section 91 (3) (a), but does not appear in the Specification as accepted. The numerals adjacent to each sequence switch contact in the drawings represent the positions of the sequence switch in which that contact is closed. For instance, the contact 109, Fig. 1, is closed in positions 2, 3, 6, 8, 9, and 10. The reverse practice is, however, followed in the case of the contacts, such as 101, Fig. 1 (one for each sequence switch), which directly control the sequence-switch motor magnet. The numerals in this case denote the positions in which the contact is open, and in which therefore the sequence switch is capable of coming to rest. Sequence - switch contacts represented in fork form, as at 209, 210, Fig. 2, are arranged to close one contact before the other contact is opened. General operation of the system. A calling subscriber is answered by an operator inserting a plug such as 134, Fig. 1, in his line-jack. The operator's listening set and master-keys are connected to the appropriated cord-circuit by a sequence switch, individual to the cord-circuit, the circuits for this purpose being shown in Fig. 2, 281 being the motor magnet. While the operator is enquiring the wanted number, a cord-finder, Fig. 3, hunts for the terminals of the appropriated cord - circuit and connects thereto the operator's key set, represented in Fig. 3 by a single row of keys 391-96, 391-98 and an associated chain of relays. The cordfinder and key-set or sender are each controlled by a sequence switch, the motor magnets of which are represented at 379, 391. The operator writes down the wanted number on her keys, and this controls the operations of selectors which extend the connexion to the terminals of the wanted subscriber. Only the first or district selector, Fig. 1, forming the other terminal of the cord-circuit of the plug 134, is represented in detail, but contacts of other selectors are shown diagrammatically at 441, 442, 443, Fig. 4. The connexions between the repeating- coils 148, Fig. 1, and 414, Fig. 4, may comprise an inter-office trunk line. The motor magnet of the sequence switch controlling the first selector is shown at 81, Fig. 1, and of that controlling the final selector, at 481, Fig. 4. As soon as the selective operations are completed, the cordfinder and sender, Fig. 3, are set free for further service. The operations, described in greater detail, are as follows. Connexion of operator's listening - set and master keys, Fig. 2, and of her impulse sender, Fig. 3, to the selector associated with the cord circuit of the answering plug 134, Fig. 1. When the answering plug 134 is inserted in the jack of a calling subscriber, the cord relay 135 is energized in series with the cut-off relay and the cord battery 150 is put into the calling line through the winding of the supervising relay 141. The cord relay 135 at contact 138 completes a starting-circuit for the magnet 281, Fig. 2, of the listening-key sequence switch, which moves at once into the fifth or listening position. In passing the second to fourth positions, it grounds at 203 a circuit 227 common to the other cord circuits of the same operator's position, so as to energize, for instance over contact 242 or 262, any other listening - key sequence switch which may be in the fifth position and move it on into the ninth or offlistening position. In the fifth position, contacts 210, 211, 213, 214 are closed to connect the operator's instruments in bridge across the cord circuit. In the meanwhile, contact 215, Fig. 2, has completed a starting circuit through the magnet 81, Fig. 1, of the selector sequence switch, which moves into the second position, in which, among other effects, a supervising- lamp 158 is lighted over contact 106, and a starting-circuit is closed through contacts 161 and 104 for the magnet 379, Fig. 3, of the cordrinder sequence switch. This also moves into its second position, closing at 304 the circuit of the cord-finder motor magnet 323, which starts the brushes 309 ... 313 hunting round for the cord circuit. When the brush 313 comes on to terminal 318, which has been grounded by the contact 102, Fig. 1, a test relay 325 connected to the brush 313 over contact 302 is energized and cuts out the motor magnet 323, energizing over its back contact the holding-magnet 324, which stops the brushes on the terminals 314 ... 318. The magnet 379 is energized in parallel with the magnet 324, and moves the cord-finder sequence switch to its fifteenth position. From the fourth to the fifteenth positions, the contact 303 energizes the relay 325 in series with a relay 365, which completes a starting- circuit for the magnet 391 of the impulse sender sequence switch, which moves to its second position. Selection of wanted line. The above operations ensue automatically on the insertion of the answering plug 134. The operator meanwhile ascertains the number of the wanted line and presses keys corresponding to the digits. Only a single selector is shown in the Figures, and a set of keys corresponding to a single digit is shown at 391 ...398, Fig. 3. It will be assumed that the eighth key 398 is depressed. At the same time, key 378 is closed to move the sender sequence switch to its third or sending position. Contact 361 now completes a circuit from grounded pole of battery 152, Fig. 1, through contact 110, lines 193, 383, relay 362, lines 382, 192, contact 125, relay 153, contact 121, back to battery 152. The relay 153 energizes, over its front contact 156 and contact 112, the magnet 81, which moves the selector sequence switch to its third position. The motor magnet 68 of the brush selector is now energized over contacts 129, 156, 161, and rotates the shaft 40, whereby the relay 362, Fig. 3, is intermittently shortcircuited at contact 60. By examining the circuits at the foot of Fig. 3, it will be seen that the first time the relay 362 is energized, it energizes relay 341, which locks up and prepares the circuit of relay 331, which is energized and locks up when the relay 362 falls back. The second energization and de-energization of the relay 362 locks up the relays 342 and 332, and so on, each energization and de-energization of the relay 362 adding a link to the double chain of locked relays 341, 331, &c. The energization of relay 338, which occurs when the shaft 40 has been turned through eight steps, closes a circuit through the depressed key 398, contact 358, and relay 363, which opens the circuit of the relays 362 and 153. The relay 153 opens the circuit of the motor magnet 68 and closes at its back contact a circuit through magnet 81, which moves the selector sequence switch to its fourth position. This energizes over contacts 170, 103, 161 the brush carriage motor-magnet 62, which rotates the brushes until one set is released from its latch 32 by the corresponding finger 41 on the brush selector shaft, and then further rotates them so as to carry the released brushes over the bank terminals. When the test-brush 25 makes contact with the test-terminal 29 of an idle line, test-relay 165 is energized over a high-resistance winding 167 and locks up over a low-resistance winding 168. As soon as the brushes come centrally over the terminals 27, 28, 29, an arm 72 slides off a tooth of the grounded plate 50, thus removing a short-circuit from the relay 166, which becomes energized in series with the test relay 165, cutting out the motor magnet 62 and energizing over its back contact the holding- magnet 65, which brings the brushes to rest. The trunk 173, 174 175, to which the cord circuit 176, 177 is now connected, is marked busy by the reduction of potential on the test-terminal 29 and its multiples, ow