Patent GB-228173-A (GB)
Title: Improvements in electro-mechanical telephone systems
IPC: H01H63/32
Filed: 1925-01-22
Abstract: 228,173. Aldendorff, F. Jan. 26, 1924, [Convention date]. Automatic exchange systems; selectors. - Spring-driven group selectors and connectors (the latter not being described in detail) are arranged to test trunks in sets and to pass over busy sets in a single step, testing of individual trunks taking place when a set containing an idle one is reached. The selectors used have more than two kinds of motion. For example, a group selector is lifted by a stepping magnet in response to numerical unpulses, then flies round until a set of trunks containing an idle one is reached, and is then moved one line at a time by a stepping magnet. A two-digit group selector is lifted by the first digit and takes a number of long rotary steps under control of the spring in response to the second, and then tests sets of trunks and individual trunks in the same way as the single-digit selector. A three-digit connector is stepped vertically, takes long spring-operated rotary steps, and then short rotary steps under control of a stepping magnet in response to successive digits, and if the line reached leads to a private branch exchange and is busy the stepping magnet continues to operate until an idle line is found under control of a fourth wiper. The selectors described have a single set of wipers and the vertical movement comes first, but several sets of wipers may be used, and the numerical impulses may produce rotary motion, subsequent fast and slow trunkhunting being done vertically. The numerical and non-numerical functions may be performed by separate switches. A selector is described in which the first impulse of a series does not affect the stepping magnet, the number dials being suitably modified. This is to prevent the selector from starting up if the calling party hangs up without dialling. In the system described a call finder is moved by a spring to the line in a single step, and if it overshoots the line is moved back to it by a stepping magnet. The group selector levels have 20 - - 50 outlets and the connector levels serve 50 lines. Specification 227,792 is referred to. Construction of switches. Group selectors and connectors are structurally similar. The. wiper shaft 1, Fig. 1. which is lifted by means of a circular ratchet 31, has a pin and groove connection with a cam disc 4 connected by a sleeve 3 to the inner end of the driving spring 22. The spring band 21 is connected by a sleeve 7 rotatable about the sleeve 3 to a ratchet disc 8 cooperating with a stepping magnet 27. In the normal rotary position, the two discs are clutched together by an armature 11 which passes through a slot in the ratchet into a slot 12 in the cam disc. When the clutch magnet 17 is energized, the cam disc (and wiper shaft) is whirled round, and when it falls back the armature 11 enters one of the slots 16 and stops the cam disc. The clutch magnet is shunted by a condenser to make it quick to release. The wipers are now given slow rotary movement by the stepping magnet 27. Release is effected by a prolonged energization of the clutch magnet. The wipers fly round until a pin 28 on the shaft engages a guide 29, in which position the detent 26 registers with a groove in the ratchet 31 and the wiper shaft drops back. When the pin 28 leaves the guide 29 the wipers are rotated further. being stopped in their normal position by a member 15 which enters a slot 12 in the cam disc. (The slots 16 are too narrow for the member 15 to enter them.) Meanwhile the stepping magnet 27 receives impulses to rewind the spring under control of off-normal springs, such as those shown in Fig. 13. These are controlled jointly by cams 328<1>, 328<3> on the cam and ratchet discs and do not restore to normal until the wipers are in the normal position and the spring is fully rewound. The clutch magnet is then released and the armature 11 forces the member 15 out of the slot 12. The member 15 is provided with a spring blade 15<1>, Figs. 10 - - 12, which prevents the member 15 from falling back into the slot 12 when next the clutch magnet is energized. The projections 32 on the cam disc control a set of springs and vary in size and shape according to the functions the selector has to perform. The sleeve 7 carrying the clutch magnet &c. is supported by a bearing 20. Call-finder, Fig. 5. Line relay 102 disconnects the subscriber's marking terminal 109, connects his test terminal to the cut-off relay 104. and energizes the starting relay 111, to energize the control magnet 118 of the allotted call-finder, and the wipers fly round under the influence of a spring. The change over of off-normal springs 117 &c. puts the magnet 118 under control of the wiper 122, and when the latter reaches the marking terminal 109 magnet 118 falls back. This terminal is reached before the other terminals of a set to give the magnet plenty of time to deenergize. The calling line may disconnect several terminals 109, and if the wipers stop beyond the line, the magnet 145 steps the wipers back to it in a circuit 147, 145, 126, whereupon switching relay 140 pulls up in series with cut-off relay 104. Line relay 102 releases starting relay 111 and the driving magnet 153 of the allotting switch is started up over and operates until the next idle finder is found. Relay 150 pulls up over a contact in the group selector and locks itself to offnormal contact 126. One-digit group selector, Fig. 6. Impulse relay 205 energizes release relay 208 and the digit is repeated to the vertical magnet 1. At the first impulse, change-over relay 220 pulls up, and when it falls back at the end, relay 222 is energized over vertical springs 219, and energizes the clutch magnet 2. The trunks from a level are divided into sets, and if the first set is busy, positive potential on the cam-operated contact 229 over the chain circuit 230 - - 233 keeps the clutch magnet operated long enough for the wipers to pass the first terminals of the, set. The chain circuits of subsequent sets are connected to arcuate terminals 240, 242, &c. co-operating with wiper 218. If the trunk 243 - - 245 is idle. the terminal 242 is dead, the clutch magnet falls back, and the clutch enters the next slot in the cam disc, the wipers then resting on the first terminals 249 - - 251 of the set containing the idle trunk. Relay 252 now pulls up in series with the clutch magnet over wiper 218, locks up and completes the interrupter circuit of the stepping magnet 3 which operates until the arrival of the test wiper 217 at an idle trunk operates the test relay 259. Switching relay 262 then pulls up and disconnects the impulse relay. Three-digit connector, Fig. 7. Impulse relay 305, release relay 310, and vertical magnet 1 operate in response to the hundreds digit in the same way as the corresponding elements in the group selector. The relapse of the change-over relay 319 energizes relay 322 over vertical springs 323 so that the tens digit is repeated over cam-operated contact 334 to the clutch magnet 2, and the wipers take a series of long steps. At the beginning of each step contact 334 disconnects the impulse contact so that the clutch enters the next slot in the cam disc and the clutch magnet is again connected to the impulse wire. The relapse of change-over relay 319 this time energizes relay 345 over rotary springs 348 so that the units impulses go to the rotary stepping magnet 3. At the first impulse the change-over relay energizes relay 351, which locks up. Hunting for an idle line to a P.B.X. The fourth terminals of P.B.X. lines other than the last of a group are connected to negative battery, those of last lines and of single lines being dead. If the connector is stepped to a P.B.X. group and the test relay 359 fails to pull up, relay 360 pulls up and the relapse of the change-over relay 319 completes an interrupter circuit for the stepping magnet 3 over 365. 363, 362. This circuit is broken by the energization of the test relay, or by the relapse of relay 360 when the last line is reached. Supply and control of ringing current. If the line is idle, or when an idle line is found, relay 359 completes an interrupter circuit for ringing relay 374 which connects the ringing generator 377 intermittently to line. When the called party replies relay 378 disconnects the ring- ing relay and energizes a back-release relay 381. Release. When either party hangs up, release relay 310 is short-circuited and unlocks relays 351, 322, 381, and the test relay 359 falls back. The clutch magnet 2 is held steadily energized until the rotary springs change-over and the wipers return to normal as described above. Meanwhile the stepping magnet 3 is operated in a circuit 353, 317, 365 to re-wind the spring. Release of the connector releases test relay 259, Fig. 6, and switching relay 262, and provided the calling party has hung up, release relay 208 is short-circuited and causes the continuous energization of the clutch magnet 2 until a changeover of vertical springs unlocks relay 222. Meanwhile the stepping magnet 3 rewinds the spring over contact 256 until the off-normal springs 227 unlock relay 252. The relapse of switching relay 140 in the call-finder, Fig. 5, causes the operation of the stepping magnet 145 until the off-normal springs change over. Two-digit group selector, Fig. 8. This is operated similarly to the connector. Fig. 7, the numerical impulses causing vertical stepping followed by long, spring-controlled steps. The long steps, however, are the length of two slots in the cam disc instead of one, the clutch magnet 423 being kept energized by the cams 32<2>, 32<3>, &c. for a suitable period after each impulse. The relapse of change-over relay 415 after the second digit energizes relay 462, which connects the clutch magnet 423 to the fourth wiper 456. If all the trunks in the first subdivision of the wanted group are busy, the clutch magnet is energized over this wiper and a chain circuit and the