Patent GB-211909-A (GB)
Title: Automatic telephone exchange
IPC: H01H63/00
Filed: 1922-09-25
Abstract: 211,909. Faller, E. A. Sept. 25, 1922. Automatic exchange systems and apparatus; selectors and associated switchboard apparatus.- A system is described which imitates the working of a manual exchange system of the " express " type using " A " and " B " boards, but in which operations equivalent to the plugging operations of the " A " and " B " operators are performed by mechanical switches. These switches are adapted to lift brush-carrying " shuttles," which correspond to the plugs in the manual system, into engagement with subscribersline or trunk-line terminals. In the 2,000-line system described, the subscribers' lines are divided into 20 exchange sections of 100 lines. The lines of each exchange section end in terminal sets in both an " originator " switch and a " terminator " switch. When a subscriber makes a call, the originator serving his exchange section selects a shuttle, associated with an idle " cordcircuit " to a " pilot " switch, and raises it to the calling line terminals. At the same time a pilot shuttle in which the selected cord-circuit terminates, is marked, and after the transmission of the thousands and hundreds digits, which are simultaneously sent over the a and b wires respectively, is lifted to an idle trunk leading to a shuttle of the terminator serving the wanted exchange section. The tens and units impulses are now simultaneously sent over the a and b wires, and the marked terminator shuttle is raised to the wanted line terminals. The originators, terminators and pilots are each provided with twelve shuttles each of which has access to all the lines incoming to the switch, thereby rendering it possible for each switch to take part simultaneously in twelve connections. Each pilot has access to five trunks to each terminator, but the trunks from the twelve shuttles of each terminator may be multipled in the pilot banks to meet any traffic requirements. A layout is described in which the 2000 lines are divided into two main 1000- line groups, seven trunks from each terminator being allotted to the pilots of the busier first group and the remaining five to those of the second group. Of the seven trunks allotted to the first 1000- line group, two are multipled in the banks of one half of the pilots of this group, two are multipled in the banks of the other half, and three are multipled in all the pilots. The five trunks allotted to the second 1000-line group are all multipled in all the pilots of that group. If all the available trunks to a terminator are engaged, a busy signal is sent back to the calling party from the pilot. Ringing mechanisms at the terminators are arranged to transmit ringing current to both the calling and called parties. For convenience in tracing circuits subsequently described, Figs. 1, 4, and 3 should be arranged from left to right in one row, and Figs. 6, 5, and 2, respectively placed below them. Construction of impulse transmitter, Fig. 1. This comprises four number rings 1 - - 4, one for each digit, mounted side by side and positioned when set to a wanted number by rollers 5 - - 8 resting in indentations in the peripheries of the rings. Within the number rings 1 - - 4 are located make-and-break wheels 19, 120, 176, 178 which are mounted on a common shaft in such a manner that during the first half revolution of the shaft. teeth on the thousands and hundreds wheels 19, 120 simultaneously engage fixed springs 18, 121 and transmit numerical impulses over the A and B wires, respectively, whilst during the second half revolution the teeth on the wheels 176, 178 engage springs 177, 179 and simultaneously transmit the tens and units impulses over the A and B wires. The thousands wheel 19 is provided with an eleventh tooth 20 which normally engages the spring 18. A disc 84, also mounted on the common shaft, has a segment 85 which normally bridges two contact springs 83, but when the shaft has been rotated half a revolution bridges two other springs 169. The shaft is rotated by a clockwork mechanism 31 which is wound by a knob 30 after the number rings 1 - - 4 have Been set, and which is automatically released, to rotate the sender shaft half a revolution at a time, by a detent controlled by a magnet 32. When the winding knob 30 is turned, a lever 21 which normally engages the contacts 24, 25, is caused to engage two other contacts 22, 23, but when all the dialling impulses have been sent it returns to contacts 24, 25. Construction of shuttle-lifting switches. The lines to which a switch has access end in terminals which are multipled in twelve vertical rows, the terminals being formed by tongues on multipling strips which extend across the bank as shown in Fig. 39. Each vertical row is served by a shuttle, a selected shuttle being raised to a wanted line by lifting mechanism. Each shuttle 307, Figs. 37, 38 and 40, is adapted to slide between a pair of vertical bars 305 and is connected to upper and lower tension ribbons which pass over spring drums 309, 310, Fig. 31. The spring of the lower drum 310 is stronger than that of the upper drum 309 so that the shuttles are normally held in their lowest positions. The upper drum 309 is provided with a ratchet-andpawl device 311 which holds the shuttle in the position to which it is lifted until the pawl is released by a magnet 312. Each shuttle carries a brush lever 315, Figs. 37 and 38, and an actuating lever 316 normally held, against the action cf a spring 316<1>, in a retracted position, as shown in Fig. 38, by the engagement of a detent 320 with a pin 319. The lever 316 is provided with a lifting tooth 317 and carries a lever 318 which serves to project or release the brush lever 315. When the switch is used as a pilot or a terminator, a shuttle corresponding to a trunk taken into use is selected by the energization of an appropriate magnet which releases the detent 320 and causes the actuating arm 316 to assume the extended position shown in Fig. 37, in which the lifting tooth 317 is projected into the path of the shuttle-lifting beam. When, however, the switch is used as an originator, an idle shuttle is mechanically selected by a device comprising a shaft 326, Fig. 40, frictionally rotated by a continuously-driven pulley 328, and carrying a number of pairs of cam-discs 327, a pair for each shuttle. Each cam-disc is provided with a tooth 331, the teeth on the pairs of cam-discs being helically arranged around the shaft 326. Above each pair of cam-discs is mounted a dog 321 capable of being moved forward against the tension of a spring 332 by the teeth of the associated cam-disc pair, which engage a pin 330 projecting on each side, of the dog 321. The dogs 321 are loosely seated and are capable also of slight upward movement. The frictionally-driven shaft 326 acting on the discs 327 causes one of the dogs 321 to be forced forward to actuate a shuttlereleasing detent 320, and when the corresponding shuttle is lifted, the dog 321, being moved upwards, disengages its pin 330 from the teeth of the cam-disc pair, and permits the shaft 326 to rotate until another pair of cam-discs meets another dog depressed by an idle shuttle. The shuttle-lifting mechanism comprises a pair of beams 291, 292, Figs 30, 31 and 35, mounted on cross-heads 300, 299 at equal intervals on two endless belts 289, 290 running over sprocket wheels 287, 288 carried on shafts 283, 286. The shaft 283 is adapted to be clutched to a source of power when the switch is taken into use. Each of the beams 291, 292 has pivoted thereon a shaft 293, Fig. 35, terminating at one end in a roller 295 and at the other end in a lever 296 carrying a pivoted detent 297. The roller 295 and the detent 297 are adapted to engage, respectively, teeth 281, 282 on vertical cylinders 279, 280, Fig. 30. The cylinder 279 is furnished with ten long teeth 281 arranged in a helix to form one complete turn, whilst the cylinder 280 carries one hundred teeth 282 arranged helically in ten complete turns, each turn being equal in pitch to the length of one of the long teeth 281 on the other cylinder 279. When the switch is used as a pilot or a terminator the cylinders 279, 280 are geared to barrels 264, 265 frictionally driven from a constantly-rotating shaft 266. Each of the barrels 264, 265 has a series of helically-arranged teeth 271, each of which is adapted to be engaged by a pawl 272, Fig. 32, mounted on a common shaft 273 and adapted to be forced by a spring 274 into the path of a tooth 271 when a detent 275, normally engaging a pin 276, is released by an associated magnet 277. By the energization of particular magnets 277, therefore, the barrels 264, 265 and consequently the cylinders 279, 280 may be stopped in arbitrary positions corresponding to the designation of a wanted line. When the switch is used as an originator, marking switches, Figs 2 and 3, position the cylinders 279, 280 as described in the next paragraph. Each shuttle-lifting beam 291, 292 has pivoted upon it a lipped bar 298, Figs. 34 and 37, which extends across the beam and is normally held in a raised position by a detent 302 on a shaft 303 which also carries a detent 304 adapted to be raised by the detent 297. When the belts 289, 290 are set in motion, the lip on the bar 298 of a beam 292, engages the projecting tooth 317 of the selected shuttle, which is taken up with the beam. On the roller 295 engaging a group-marking tooth 281 on the cylinder 279, the detent 297 at the other end of the shaft 293 is projected into the path of a line-marking tooth 282 on the cylinder 280, the engagement of this tooth 282 causing the other end of the detent 297 to release the detent 302, which permits the lipped bar 298 to rockdownwardly under gravity. In the continued upward movement of the beam 292 a curved lever 323 (of which there is one mounted on the beam 292 for each shuttle) engages the projecting arm 319 of the raised shuttle and forces it into its inner posi