Patent GB-173009-A (GB)
Title: Telephone systems
IPC: H04Q3/42
Filed: 1920-08-10
Abstract: 173,009. Western Electric Co., Ltd., (Western Electric. Co., Inc.). Aug. 10, 1920. Semi - automatic exchange systems.-In a system in which an operator at a manual exchange controls automatic selectors at other exchanges, the depression of a key corresponding to the wanted exchange sets in action a link circuit 117, Fig. 1, which connects itself to the operator's keyboard &c. 113, selects an idle register-sending- equipment 122 from a series common to all the operators, selects an idle trunk to the wanted exchange 110, and causes the number of this trunk to be illuminated on a lamp indicator 116 at the operator's position. The operator connects the calling subscriber 200 by a cord 112 to the designated trunk and writes down the wanted number on her keyboard to register it on the sender 122, which controls the selectors 123, 124, to establish the wanted connection. The trunk indicator is released as soon as the cord has been plugged into the designated trunk, and the link circuit and sender are released as soon as the numerical operations of the selectors 123, 124 have been completed. The link circuits are arranged in groups, each group being common to all the operators but individual to the trunks to a particular exchange. An allotting switch 121 is provided for each group to pre-select an idle link circuit. Operation of the link-circuit switches 300, 400, 401, Fig. 3. The operator, having ascertained the connection wanted by a subscriber 200, Fig. 2, presses a key 114, Fig. 6, corresponding to the wanted exchange, which energizes an exchangedesignating relay 205 and relay 207, which lock themselves up and ground the circuit 238, so as to unbalance a polarized relay 301, Fig. 3. Relay 301 closes a circuit for relays 305, 405 of the link circuit pre-selected by the allotter 121, and relays 305, 405 lock themselves up and energize relays 306, 415. Circuits are now completed for the stepping-magnets 308, 416, 408 of the switches 300, 400, 401 through the test wipers 325, 428, 425, and the switches advance as long as these wipers are on grounded terminals. The switch 300 stops when it reaches terminals of the operator's position at which the key 114 was depressed, the test circuit at this position being grounded not directly through a back contact of relay 205 but only through a resistance 230, which prevents the magnet 308 from becoming energized, and a highresistance relay 310 which was hitherto short-circuited through a test wiper becomes energized in series with magnet 308. Relay 310 energizes relay 313, which grounds the circuit 332 so as to de-energize relay 301 by restoring the balance of its circuits. The switch 401 stops when wiper 425 reaches the ungrounded terminal of an idle sending-equipment, and a high-resistance relay 410, which was hitherto short-circuited over the test wiper, is energized in series with magnet 408 and energizes relays 413, 315, 316. Relay 316 de-energizes relays 306, 310, but relay 306 is slow to release, and for a short interval tone current from a source 328 is connected through circuit 334 to coil 223, Fig. 6, by which it is inductively transferred to the operator's listening-set, as a signal that she may commence operating her keyset. The switch 490 stops when it reaches an idle trunk, such as 507, 508, Fig. 2, leading to the wanted exchange, and a high-resistance relay 417, which was hitherto short-circuited over the test wiper, is energized in series with magnet 416 and energizes relays 422, 320, 420. Relay 420 connects relay 406 over circuit 453 in series with both windings of relay 505, Fig. 2, which becomes energized but is of too high resistance to allow the energization of relay 406. Operation of the trunk-indicator, Fig. 7, consisting of hundreds, tens, and units series of lamps. The hundreds lamps are controlled by a group of four relays 602, 604, 601, 603, the energization of these relays in any given combination energizing a corresponding lamp, and the tens and units lamps are similarly controlled by relays 607 - - 610 and 611 - - 614. The hundreds indication is controlled by the potential applied at points 521, 522, Fig. 2, to the wires 441, 445. Thus, in the case of trunk 507, 508, these potentials are direct ground at 521 and ground through a resistance at 522. As soon as the switches 400, 300 completed their operations, the wire 441 was connected through a circuit 340, 252 to the hundreds relays 602, 601 and wire 445 through circuit 343, 251 to relays 604, 603. Relays 601, 603 are marginal and do not respond in series with a resistance such as that at the point 522, so that in this way a particular combination of the hundreds relays is energized and the energized relays lock themselves to a wire 236. The tens and units indications are controlled by the constantlyrotating code switch 510, Fig. 2, which comprises a series of contacts arranged as shown and connected to ground. When this switch next passes through its normal position, contact 512 closes circuits for energizing relays 509, Fig. 2, and 226, 227, Fig. 6, which have the effect of connecting brushes 513, 514 through circuits 441, 340 and 445, 343 to relays 231, 229, Fig. 6. The brushes 526 - - 529 then successively engage contacts 537 - - 540. Contact 537 closes circuits for energizing the tens relay 607, provided relay 231 is energized at the same moment by the engagement of brush 513 with a contact on the code switch, and for energizing the units relay 611, provided relay 229 is energized at the same moment by brush 514; in the same way contact 538 closes a circuit controlled by brush 513 for the tens relay 609 and a circuit controlled by brush 514 for the units relay 613; and similarly with contacts 539, 540. Thus the tens and units relays are energized in combinations which depend on the distribution of the contacts in the paths of the brushes 513, 514; it will be understood therefore that the wire 441 of a given trunk is connected by relay 509 to a brush corresponding to the tens digit of the trunk number and wire 445 to a brush corresponding to the units digit. Finally, a contact 640 energizes relays 206, 228, Fig. 6, which supply current to light the selected lamps. Release of the trunk-indicator. The operator plugs into the designated trunk, energizing relays 520, 502. Relay 520 short-circuits the high-resistance winding of relay 505 so as to energize relay 406, Fig. 3, which results in the unlocking of relays 305, 313, 320 and of relays 205, 207, Fig. 6, and relay 207 unlocks the indicator relays. By the de-energization of relays 205, 313, both balancing circuits of relay 301, Fig. 3, are opened, so that the operator may start a second link circuit into operation. Recording the wanted number on the sending- registers, Fig. 4, by the operators key-set 113, Fig. 6. In the meantime, before the operator has plugged into the designated trunk, or even before this trunk has been selected by the switch 400, the operator may have proceeded to write down the wanted number. The sending registers are of the relay type, each register requiring only the duration of a single current impulse for its operation, so that only a single row of keys need be provided and these are of the non-locking type. The wires 346, 347, 334, Fig. 6, controlled by these keys are connected through switches 300, 401 to wires 622, 623, 624, Fig. 4, which, at the commencement of the recording-operations, are connected to the thousands register relays 802 - - 805. The depression of a key connects the wire 346 to ground either directly or through a high resistance 260 or through a high or low resistance winding of relay 221, so as to energize or not to energize the marginal relay 802; the key may also ground, directly or through a high or low resistance, the wire 347; so as to energize either or neither or both of the relays 803, 804, one of which is marginal; and if relay 221 has been energized in either of these circuits a circuit 334, 624 is also closed to energize relay 805. Thus according to the key depressed to represent the thousands digit different combination of the relays 802 - - 805 are energized and lock themselves to wire 736. Whatever key is depressed a relay 715 is energized in the circuit of relay 802 and energizes a relay 705, and when the key is released the de-energization of relay 715 removes a short-circuit from relay 704, which becomes locked in series with relay 705 and energizes relay 712, which switches the controlling wires 622, 623, 624 from the thousands register relays 802 - - 805 to the hundreds register relays 806 - - 809. The next depression of a key therefore energizes a particular combination of the hundreds relays and when the key is released relays 706, 713 are energized and switch the controlling wires to the tens relays 810 - - 813, and so on. The contacts of the relays in each register are interconnected so that the energization of a given combination of relays closes one of the circuits indicated by the figures 0 - - 4 in circles, these circuits being connected as shown at the bottom of Fig. 5 to different points in a chain of connecting-relays. Control of the selectors by the sending-registers, Fig. 4, and the relay counting-chain, Fig. 5; system of translation. The distant exchange is assumed to have a capacity of 10000 lines and to be equipped with incoming selectors 123 and final .selectors 124 of the 500-point type. The selector 123 first selects one out of 5 groups of 2000 lines, under control of the thousands digit, and then selects one out of 4 groups of 500 lines under joint control of the thousands and hundreds digits. The selector 124 first selects one out of 5 groups of 100 lines, under control of the hundreds digit, and then completes the connection by two further movements under control of the tens and units digits As soon as the switch 400 has found an idle trunk and the thousands digit has been registered