Patent GB-304820-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/58
Filed: 1927-10-26
Abstract: 304,820. Automatic Telephone Manufacturing Co., Ltd., Passmore, W. O., and Taylor, R. Oct. 26, 1927. Automatic and semi-automatic exchange systems.-In a system including satellite exchanges, each satellite has a particular exchange name and each subscriber therein has a four-figure number irrespective of the number of subscribers in the exchange. Each satellite comprises a discriminator having three register switches, and when a subscriber calls he is connected to a repeater which is then connected over pre-selected line-finders to a discriminator and a local selector, and over a line switch to a main exchange trunk. Direct trunks to nearby satellites are connected to terminals of local selectors, and the register-switches are connected to the terminals of a distributing frame IDF, Fig. 3, which are so connected as to distinguish between local, nearby, and main calls, and then to complete, release circuits for the discriminator and either the main trunk or local selector. The dialled impulses are repeated both to the main exchange and the discriminator, and the latter may perform its function after one or two code digits. The contacts of wiper 177, 185 of registers X, Z. Fig. 3, are connected to the levels 1, 2 and 16, 17 of the IDF in accordance with the digits marked thereon. Similarly the contacts of wipers 179 - - 183 are connected to vertical rows of terminals in levels 4 - - 13 beneath the terminals of level 3 connected to the said wipers. Levels 14, 15 are connected to the marked armatures ,and front contacts of relay PS. The terminals of row 20 are multiplied so as to form circuits for completing the operation of the discriminator after one or two code digits. In calls to 4-digit satellites directly reached, the third code digit operates the local selector, while for 3- digit satellites, the first numerical digit performs this operation. In the case of a call to a manual exchange, release is controlled by the operator. A timing device operates to release the main exchange trunk and switch through to the local selector in case of a permanent loop or delayed dialling. An alarm is given if a register switch remains off-normal. All the repeaters are busied if there is no available discriminator or local selector, and statistical meters are operated. Operation of finder-switches DRF, SRF and distributors SRA, DA. When the subscribers tine-switch seizes repeater R, relays A, B operate, relay MK energizes and locks up, operating start relays DL, SL over conductors 100, 101 and wipers 154, 156 of DA, SRA. Magnet DM3 operates in series with relay SK, which is shorted by earth over armatures such as 19, 45, and wipe.r 76, whether a repeater is busy or not. The finder SRF steps on to find R, when relay SK operates, disconnecting relay SL, during the slow release of which relay SA operates and locks up, completing a holding circuit for relay SK to earth, at armature 19. The allotter SRA now hunts for an idle finder [earth, 67, 61, 107, wiper 157, 162, DM8, battery]. The finder DRF and the allotter DA operate similarly, relays DK, DA being, held at the finish, and relay DL being released. The holding circuit for relay SK is now transferred at sptrings 35 over wipers 80, 81 and armature 141 to the contol of relay DK. Operation of junction-finder. The finder JF now steps to find a, free junction first in a circuit [19, 44, 33, 39, contact and wiper 71, 54, 58, DM1] and then to earth on the c wires of busy junctions, after which relay JK energizes, extending the repeater leads to the junction, which is looped through impedance relay I and the line winding of relay D. Dialling. Relay AA in the discriminator D now operates from earth at 15 over wiper 77, and energizes relay BB. Impulses are repeated by relay A, Fig. 2, at 14, over the junction, relay C forming a, clean loop over the junction at 21, and at 15 -:o relay AA. Relay CC operates throughout a digi and two-step relay DW operates the first break-and-make at 109. The first pulse is thus absorbed, the remainder of the digit being registered on switch X. Two-step relays DX, DY, energize in turn to route the second and third digits to switches Y, Z, and relay DZ thereafter. Local call. If the satellite is Colbrook. the digits 205 will have been dialled, and X. Y, Z, will be on 2nd, 11th, and 6th contacts respectively. Release relay RA of the discriminator now energizes in parallel with switching relay LS, Fig. 2 [earth 113, wiper 177. and contact IDF. level 1 to 3, wiper 179 and contact IDF, level 13 to 16 contact and wiper 185, (a) RA, (b) 143, 95, 79, 39, LS]. Relay DK is released at 133. relays AA, BB, DW - - DZ, release in turn, and switches X, Y. Z home in turn. Relay BP operates, in series with the switch magnets to maintain RA energized, so that if any switch sticks an alarm is operated in series with lamp 200. Relay LS, switches the repeater leads to wipers 73, 74 and the numerical digits are. repeated to the local selectors, the junction being released. Relay SK is now held over armatures 42, 19, and JK is maintained over the original circuit of LS until BB restores to guard the junetion during release.. Calls to four-digit exchanges directly reached. The first two code digits control the operation, and after switches X, Y are set, relay PS operates over tie switches and the IDF, and locks up, and a circuit is formed from earth, 108, wipers 78. 73, 104 to one winding of the local selector line relay, to which the third code digit is. repeated, as well as to D and the main office. After the third digit, the discriminator and the junction are released as before and, the numerical digits are repeated over the local selector to the desired exchange. Call to or through main office. This is. determined by one or two code digits. The first and second code digit IDF terminals. for such calls are all jumpered to the terminal row 20, and as soon as CC releases after the first digit, relay RA operates over said terminals, but not relay LS. so that when relays DK, AA, BB have releases in turn, SK restores, releasing the local line, and the call is completed over the main junction. Call to three-digit exchange directly reached.. The switch-over to local switches and release of main junction takes place after the three code digits are dialled, and the first of four numerical digits operates the selector to find a line to the exchange. Wanted subscriber busy. The circuit of relay MH is normally open at 28, but during thesimplex battery period of the busy signal, relay I restores, and MH energizes and locks up, holding relay B at 30. During the tone period, MH is shunted. When the calling subscriber hangs up, the repeater restores during the next tone period. Completion of connection; release. On reply, shunt-field relay D energizes to operate the, meter over conductor 10, relay MK being released. When the caller hangs up, relay A opens the outgoing loop, and relays C, MK temporarily energize in turn during the release of relays B, C to guard the repeater during release of the switch train. Switch JF is homed and the remaining relays released. Call to manual office, such as a toll exchange. The operator puts battery on both lines, relay MH operating and connecting earth to relay I. Release of relay A will remove earth from the upper junction wire to control the operator's cord signal, the operator holding the switch by means of relay MH, which holds relay B. Permanent loop or delayed dialling. When a discriminator is seized, relay S operates over wiper 160 of the delay equipment DE, locks up over armature 118, 114, and energizes start relay ST of DE. Intermittent earth on 174 now energizes two-step relays PT, PR in turn, connecting half-minute pulses to relay P, which operates magnet DM8. After five steps, relay Z in the discriminator operates over wiper 159 and locks up, releasing relay S. and rhe equipment DE. Earth at 149 row operates relays LS, RA in parallel to release the discriminator and the main junction, switching through to the local selector to identify the repeater. If dialling takes place during the operation of DE, the circuit of relay S is cut at 118 to release the equipment, which steps to the next home position over wiper 158. All discriminators or local lines busy. Statistical metering. Earth over chain circuits comprising armatures 145, Fig. 3, or 65, Fig. 2, energizes relay CB to busy all the repeaters, and congestion meters are operated over 188 or 189.