Patent GB-283201-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1927-12-14
Abstract: 283,201. Associated Telephone & Telegraph Co., (Assignees of Wicks, J.). Jan. 7, 1927, [Convention date]. Automatic exchange systems. - Single-motion switches of line-switch type are employed as group selectors and connectors and are set numerically under the control of register-controllers to which they transmit reverting impulses. The switches are provided with two sets of wipers set at 180‹ apart so that each set becomes operative when the other moves out of the bank. Each set of wipers engages a different bank of contacts, and each bank is divided into five groups of eleven lines, so that the whole switch serves ten numerical groups. Figs. 1 - - 5 show a partyline system employing group selectors S<1>, S<2>, Figs. 1, 4, and connectors C of step-by-step single-motion type set under the control of a, register-controller, Figs. 2, 3. The initial circuit of the line relay of each switch includes a back contact of the release relay which is short-circuited by the line relay when it operates. The release relay locks to the third wire independently of the line relay, this arrangement resulting in the release of the line relay at the end of the group-selecting operation to effect circuit charges which initiate the line-selecting operation. The selection, of and the connection of the appropriate ringing-current is effected in the register-controller which makes a test over one of the talking conductors, and if the wanted line is busy immediately releases itself. Reverting party-line calls are set up by selecting a revert. ing call switch RV, Fig. 5, which is also of the single-motion type and similar in its two-digit operation to the connector C, the setting of this switch determining the connection of the appropriate ringing-currents for ringing the calling and called parties alternately. Provision is made for calling an operator's circuit by dialling a twodigit number, and both in this case and also in the case of a reverting-call the setting of the register-controller causes the condensers at the first-selector feed-bridge to be cut out. The system also includes means for giving a busy tone if all trunks in a wanted group are busy and means for releasing the register-controller after a predetermined time interval, the latter being effected by means of a marginal relay 34 which responds to an increase in current over the lead 95. Fig. 6 shows a modification in which the selectors and connector are power-driven, the latter having fast and slow speeds for tens and units selection, respectively. Other features of the system described herein are claimed in divided Specifications 294,618 and 304,702. In the following description, it is assumed that subscriber AS on a ten-party line is extending a call to subscriber B<5> (No. 27085). Seizure of register-controller and registration of wanted number. Line switch LS operates in the usual manner, and release relay 32 of the first selector completes a circuit over the lower winding of relay 34 for switching relav 72 of the register-selector RSS. When an idle register-controller is found, relays 72, 206, operate. The four numerical digits are then repeated in the usual manner to the digit-registers 320 - - 323 whilst the station digit, passes to the magnet 341 of the frequency-selector FS. First and second selectors S<1>, S<2>. When the first digit has been registered, the relapse of relay 312 completes a circuit over wiper 346 for relay 209 which connects relav 207 in series over conductors 97, 96, 22<1>, 25<1>, and back contact 118 of release relay 107, with the line relay 106 of the first selector S'. Relay 106 locks up to conductor 25<1> and energizes release relay 107 which locks to conductor 23. Magnet 108 now rotates wipers 131 - - 136 and during their passage over the last five contacts of each group cam 121 completes a local circuit for the line relay, at the same time short-circuiting relay 207. The successive operation and release of relay 207 controls a counting chain consisting of five two-step relays 351 - - 355 so that after two impulses have been sent back, a circuit 365, 332, 325, 347, 257 is completed for relay 208 which opens the impulsing loop and energizes the stepping magnet 345 of the sequence, switch SO. The opening of the local circuit by cam 121 when wipers 131 - - 135 arrive at the beginning of group 2 releases line relay 106 and completes a hunting circuit for magnet 108 over contacts 119, 110 and wiper 133. When an idle trunk is found, switching - relay 105 operates and extends the connection to the line relay 406 of the second selector S<2>. A short time after the advance of wiper 347 of switch SO. relay 208 falls back, and if by this time the second digit has been registered, relay 209 energizes again over wiper 346 and contacts 392<1>. 317, and the setting of selector S<2> takes place in a similar manner to that of selector S<1>. Connector C. When the impulsing circuit has been extended to an idle connector, relays 457, 456 operate in a similar manner to that of relays 106, 107, Fig. 1, and the setting of the connector for the tens digit is similar to that already described for the numerical operation of selectors S', S<2>. Since the tens digit in this case is 0, the wipers make one complete revolution and again make contact with the first (dead) contact of group 0. At the end of this digit relay 457 releases and the impulsing circuit is extended over back contact 472 to a slow relay 459, interrupter contacts 460', and magnet 460. The latter does not operate, but relay 459 pulls up in series with relay 207 and energizes a slowrelease relay 459<1>, which remains operated during units impulsing. Relay 459 completes a direct circuit for magnet 460, thus short-circuiting itself and relay 207 and causing magnet 460 to open its interrupter contacts and advance the wipers one step- When relay 459 relapses, relay 207 re-operates and further impulses are transmitted in a similar manner until relay 208 operates to open the impulsing circuit. Called line busy. During the units setting, the test relay 458 is connected by relay 459<1> to the test wiper 483 so that if the called line is busy relay 458 is operated and, on the release of relay 459<1>, is locked in series with switching relay 455 to conductor 453. In the register-controller, the operation of relay 208 at the end of the units digit energizes relay 204 which connects a test relay 203 to the lower talking conductor, relay 210 being operated in series with relay 209 over wiper 346. Since relays 455, 458 at the connector have connected battery over magnet 460 to conductor 454, relay 203 energizes and connects earth over resistance R and lead 94 to the upper windings of relays 35, 36. The former operates and completes the through connection from busy lead 480, Fig. 4, to the calling subscriber, at the same time releasing relays 72, 206, the latter completing circuits for the release magnets of all the switches in the register-controller. Called line idle; party-line ringing. If the called line is idle switching relay 455 operates over wiper 483 in series with relay 495 and magnet 497. Since at this time there is no battery connection to the lower conductor 454, relay 203 does not operate, but on the relapse of relay 204 ringing lead 80<1> is connected over wiper 343, lead 251, ring-cut-off relay 201 and leads 97, 22<1>, 452 to earth at the subscriber's bell (reversing relay 202 being operated for station digits 1 - - 5 over wiper 342 of the frequency-selector FS). When the called subscriber replies, relay 201 operates and completes the switching circuit over lead 94 for relay 35 which switches through the talking circuit and releases the register-controller as before. Metering. The back-bridge relay 33 shortcircuits a resistance 45 which was connected in series with the meter 18 by the release relay 32. This resistance is sufficient to prevent the meter from operating but is not sufficient to de-energize it when once operated in case the called party should inadvertently operate his switch hook. Release. When the calling party hangs up, the relapse of release relay 32 releases switching relays 5, 35, 105, 405, 455 and release relays 107, 407, 456. In the selector S<1> a restoring circuit is completed over off-normal springs 123 for magnet 108 and during the restoration other offnormal springs 122 maintain earth on the release conductor 23. Similar restoring operations occur in selector S<2> and connector C. Reverting call. Subscriber A<6> wishing to call subscriber A<2> dials the number 2138. The first two digits control selectors S<1>, S<2> as before to seize an idle reverting call switch RV, Fig. 5, and the two final digits determine the alternate. transmission of ringing current to both calling and called parties, switch RV being set by these digits in a similar manner to the connector C. At the end of the fourth digit, however, relay 303 energizes in series with relay 208, a short-circuit from this relay having been removed by the operation of relay 348 over wipers 324, 326 of the first two digit registers. Relay 303 connects relay 388 to earth over conductors 262, 97, 22<1>, 442 and armature 537, and relay 388 operates. At thet switch RV, relay 507 (corresponding to relay 459, Fig. 4), has energized slow-release relay 508 during the final digit, and the latter has energized a further slow-release relay 509 and partially energized a two-step relay 504. At the end of the digit, the relapse of relay 508 operates relay 504 completely, causing the release of relay 388 whereby direct earth is connected to switching lead 252, 94. Over this circuit relays 35, 36 respond, the latter cutting out the talking condensers 52, 57 and completing a metallic connection through the feed group TRG to the switch RV. Relays 31, 32, 35 and the register-controller are released but ground is maintained on the third wire by relay 509.