Patent GB-142851-A (GB)
Abstract: 142,851. Western Electric Co., (Assignees of Lundell, A. E.). Aug. 17, 1916, [Convention date]. Semi-automatic exchange systems.-An indicator for showing the number of a wanted subscriber is operated over the two sides of a trunk circuit (with earth return) by impulses varying in duration and order, or in duration, order, and number. The indicator consists of four sets of ten lamps, Figs. 5, and 6, for the thousands, hundreds, tens, and units digits, each controlled by a group of seven relays, and a set of six " station " lamps, shown in Fig. 4, controlled by a group of six relays. According to which relays in each group are energized, a circuit is closed for lighting one lamp in each set. The groups of relays are successively controlled by a ratchet-operated multi-position switch, having two arms 420, 421, Fig. 4, which are moved one step both when the magnet 400 is energized and when it is de-energized. The magnet 400 and the circuits over the arms 420, 421 are controlled by two selecting- relays 401, 402, which are connected to the two lines of the incoming trunk circuit 301, 302, Fig. 3, the arrangement being such that the armature of magnet 400 is only attracted when both its windings are energized due to the simultaneous excitation of relays 401, 402, but is retained by current in either winding. The simultaneous energization or de-energization of relays 401, 402 is thus necessary to step forward the switch arms 420, 421, whereas the closure of a circuit over one or other of these arms, for one of the relays controlling the indicator lamps, is effected only when one of the relays 401, 402 is energized and the other is not. The invention is' described as applied to a semi-automatic system in which a calling-line. Fig. 1, is extended over a numerical switch 122, 123, under control of an operator's equipment, Fig. 2, to a trunk line 301, 302, Fig. 3, terminating at the distant exchange in a plug 303, and associated with the number-indicator shown in Figs. 4 and 5, Fig. 4 being arranged below Fig. 3, and Fig. 5 to the right of Fig. 4. The semi-automatic operator's equipment comprises keys (not shown) and a set of counting- relays, shown at the top of Fig. 2, for controlling the switch 122, 123, Fig. 1, and also five sets of keys for transmitting the number of the wanted line to the distant operator. The number recorded on these keys is registered in the usual manner on registers 201 - - 205 under control of cut-off relays 206 - - 210. The registers 201 - - 204 have additional contacts 227, 229; 234, 235; 232, 237; and 238, 240 respectively, which prepare earth connexions for the six leads a - - f, in accordance with the code representation of the depressed keys. Thus, if the thousands key 5 is depressed, the contact 227 prepares earth connexions for leads a, b, c and contact 229 prepares a similar circuit for lead c. These earth connexions for the several registers 201 - - 204 are completed in succession by the contacts 228, 233, 236, 239 of the controlling sequence switch 200 as it moves from position 5 to position 13. During the signalling of each digit, the leads a, b, care successively connected by contacts 224, 230 bottom, and 230 top to the lead 111, and the leads d, e, f are successively connected by contacts 226 bottom, 226 top, and 223 bottom to the lead 112, and between such successive connexions the leads 111, 112 are directly earthed over contacts 225 and 223 top. Impulases which vary in duration, order, and number are thus impressed upon the leads 111, 112 (and therefore upon the relays 401, 402) in accordance with the number registered. The register 205, for signalling the " station " number of the wanted line, similarly has a contact 221 which earths certain of the contacts 219 top, 224 top, 222 top, and 222 bottom, in accordance with the station key depressed, thereby earthing the leads 111, 112 according to code, as the sequence switch 220 moves from position 3 to position 5. The operations in further detail are as follows :-After the insertion of the answering-plug 106, Fig. 1, the operator depresses the starting-key 105 to move switch 100 into position 2, and then depresses keys according to the number of the wanted line. When all the registers 201 - - 205 have been set, the controlling sequence switch 200 moves into its second position, in which the set of counting-relays shown at the top of Fig. 2 controls the operation of the switch 122, 123 in accordance with the setting of a set of keys (not shown). The switch 200 then moves to position 11, connecting the leads 111, 112 to the trunk circuit 301, 302, and the switch 200 moves to position 3. Relays 401, 403, 402, Fig. 4, are now energized, magnet 400 moving switch 420, 421 into its position 1. Relays 213, 214, Fig. 2, are also energized, causing sequence switch 200 to move continuously from position 3 to position. 13. During the movement from position 3 to 5, one of the six lamps shown in Fig. 4 is selected under control of register 205, but it will be convenient to describe in detail only the selection of the thousands lamp, Fig. 5, which takes place as the switch 200 moves from position 5 to position 7, the selection of the hundreds, tens, and units lamps taking place in a similar manner as the switch 200 passes through positions 7 to 9, 9 to 11, and 11 to 13 respectively. As the switch 200 moves from position 4“ to position 5, the leads 111, 112 are both disconnected from ground so that relays 401, 402 both de-energize, causing magnet 400 to de-energize and move the switch arms 420, 421 to position 2. It will be assumed that the thousands key 3 has been depressed, so that when the sequence switch 200 closes contact 228 in its fifth position, the register contact 227 earths leads a, b, and the contact 229 earths lead f. As the switch 200 moves into position 5, lead 111 is earthed over contact 224 bottom and lead a, but there is no earth connexion for lead 112 over contact 226 and lead d since this is not earthed for digit 3. Relay 402 is therefore energized but not relay 401, whereby a circuit is' closed over arm 421, wire 430, relay 506, Fig. 5, wires 429, 428, and off-normal contact 423. Relay 506 locks up independent of arm 421. When the switch 200 reaches position 5“, leads 111, 112 are earthed over contacts 225 and 223 top, thereby energizing relays 401, 402, which cause magnet 400 to move switch arms 420, 421 into position 3, but no circuit is completed over the arms 420, 421. As the switch 200 reaches position 5¢, lead 111 is earthed over contact 230 bottom and lead b, but lead 112 is not earthed. Relay 402, but not relay 401, is therefore energized, completing a circuit over arm 421, wires 431, 508, relay 500, wires 533, 429, 428 and contact 423. Relay 402 also maintains the circuit of magnet 400. Relay 500 locks up in series with relay 501 so as to be independent of arm 421. When the switch 200 reaches position 6, leads 111, 112 are again earthed over contacts 225 and 223 top, energizing relays 401, 402, but without effect since magnet 400 is already energized. As switch 200 reaches position 6“, lead 112 is earthed over contact 223 bottom and lead f, but lead 111 is not earthed. Relay 401, but not relay 402, is thus energized, completing a circuit over arm 420, wires 432, 512, relay 503, wires 583, &c. as before. Relay 503 locks up in series with relay 504. This completes the transmission of the thousands digit, and as the switch 200 moves to position 7, the circuit over both leads 111, 112 is opened and magnet 400 moves the switch arms 420, 421 into position 4 to prepare for the transmission of the hundreds digit. In the case assumed, the relays 500, 501, 503, 504, 506 have been energized, thereby prepaxing the circuit of the thousands lamps 3. The circuits of the hundreds, tens, and units lamps' having been similarly prepared, the arm 421 reaches its final position, in which contact 425 completes the circuit of the lamp and also energizes a relay 300, which extends the trunk to the plug 303. On the insertion of the plug, the relays 305, 308, 309, restoring-magnet 418, and relay 307 are energized in succession.