Patent GB-227792-A (GB)
Title: Improvements in selectors and telephone systems operating with selectors
IPC: H01H63/32
Filed: 1924-09-18
Abstract: 227,792. Aldendorff, F. Jan. 14, 1924, [Convention-date]. Automatic exchange systems; selectors.-Relates to spring-driven switches in which a toothed wheel on the wiper shaft co-operates with the armature of an electromagnet, which on pulling up allows the wipers to be whirled round and on falling back stops them. The selectors are used as call finders, group selectors, and connectors. During hunting the control magnet is energized over a fourth wiper and a terminal row separate from the ordinary test terminals. The control magnet is made quick acting by shunting it with a condenser or by causing it to cut a resistance into its circuit or by providing it with a de-energizing winding with more ampere turns than the energizing winding. In the case of a call finder two or more terminals in the extra row may be marked by the calling line, and if the wipers stop on a wrong line they are moved to the right one step by step. The marking terminals are staggered between the other terminals (or a similar displacement is given to the fourth wiper) to give the control magnet as long as possible to fall back. A group selector is described which is moved vertically by a stepping magnet and is then whirled by a spring to an idle line. A long and short step group selector is described also, in which the control magnet is kept energized between impulses over contacts controlled by a cam disc on the wiper shaft, and during hunting over the fourth wiper. In a connector working on a similar plan, the long tens steps are controlled by the fourth wiper and the units steps by an interrupter disc on the wiper shaft. Construction of switches. The selector shown in Fig. 1 can be used, with slight modification, either numerically or non-numerically. The wiper shaft 1 is held against the action of a spring barrel 9 by a detent 18 engaging a ratchet disc 17 and withdrawable by the control magnet 19. The spring barrel is re-wound by ratchet and pawl mechanism operated by a magnet 15 which is controlled by wipers 21, 22 engaging slip rings on the disc 17. The slip rings are normally connected together but are disconnected by a pin 24 and cam 23 when the barrel is fully wound. Cam discs for controlling interrupter springs are provided on the wiper shaft in the case of group selectors and connectors. The wiper shaft may be movable also by a stepping magnet acting on the disc 17. The two-motion switch shown in Fig. 1<a> is similarly controlled as to rotary motion, but the shaft 1 can be lifted by a circular ratchet 27 and engages the disc 17<1> through a pin and groove 30, 29 or an arm and fork 41, 40. The selector is restored by allowing the wiper shaft to fly round until a pin 31 engages a guide 32. The detent 33 then registers with a groove in the ratchet 27 and the wipers drop back and are given a slight further rotation when the pin 31 leaves the guide 32. Call-finder, Fig. 2. The energization of line relay 40 of subscriber S, disconnects the two marking contacts 48, 49 from positive battery, connects the cut-off relay 43 to the test terminal 51, and energizes the starting relay 90. Relay 90 energizes the control magnet 19 of the finder shown over wiper 54 of an allotting switch, and the wipers fly round. The operation of off-normal switch 25 energizes relay 56 so that the circuit of magnet 19 depends on the extra wiper 58, and when the marking terminals 49, 48 are reached, magnet 19 falls back and stops the wipers. If the wipers stop on the terminals preceding those of the calling line, magnet 19 completes at 69 a selfinterrupting circuit for itself and allows the disc to escape one tooth, whereupon a circuit is made over test wiper 59 for the cut-off relay 43 and switching relav 72. The relapse of the starting relay 90 completes an interrupter circuit for the magnet 88 of the allotting switch. In a modification the marking terminals preceding and following the calling line are marked, and if the wipers overstep the calling line they are stepped back by a separate stepping magnet. Two-motion group selector, Fig. 3. The switching through of the talking wires results in the successive energization of impulse relay 202 and release relay 203. The hundreds digit is repeated to the vertical magnet 28. The first impulse removes a short-circuit from change-over relav 214, but at the end of the digit it is again short-circuited and completes a circuit over vertical springs 218 and rotarv spring 221 for the control magnet 219. The wipers fly round until an idle connector is found. the change-over of rotary springs 223 having put the magnet 219 under control of the extra wiper 213. Switching relay 226 now pulls up over the test wiper 212 and releases the impulse relay 202. Single-motion group selector, Fig. 3<a>. In this case, impulse relay 301 repeats the digit to the control magnet 319. As soon as the wipers move at each impulse a circuit is made for magnet 319 by the cam disc 300 and is maintained until the wipers have completed a long step. The relapse of the change-over relay 330 energizes relay 333 over off-normal contact 334 so that the control magnet is connected to the extra wiper 325, and an idle connector is selected as in the previous case. Connector, Fig. 4. When the talking wires are switched through, impulse relay 402 energizes release relay 403. The tens impulses are repeated over the extra wiper 414 in its positions 410, 422, &c. to the control magnet 419. After the first movement following each impulse, the magnet 419 is held over intermediate contact arcs such as 421 which are permanently connected to negative battery, so that the wipers take a number of long steps. At the end of the digit, change-over relay 424, which pulls up at the first impulse, is shortcircuited and falls back, and relay 427 pulls up over off-normal contact 430 and connects the impulse wire 431 to the control magnet over the cam-operated interrupter 433. The wipers are therefore moved in response to the units digit one line at a time. The energization of relay 424 on the first impulse energizes relay 437, which locks up and its relapse connects up the last relay 436. The interrupter 433 mav be replaced by a contact operated by the control magnet. Supply of ringing current. If the line is idle, relay 436 completes the interrupter circuit of ringing relay 445, and ringing generator 448 is intermittently connected to the line. The energization of supervisory relay 449 when the called party replies, disconnects the ringing relay and energizes a back-release relay 451. Release. When either party hangs up, release relay 403 is short-circuited (over either 453, 454, or 457) and connects up control magnet 419 over off-normal contact 464, and rewinding magnet 415<1> over off-normal contact 460. The latter contact is controlled by the relative positions of the wiper shaft and spring barrel. The release of the connector releases the switching relay 226 (or 336), Figs. 3 and 3<a>, and if the calling party has not hung up, release is held up by the re-energization of the impulse relay 202 (or 301). This can, however, be avoided by the provision of a further relay. When the impulse relay falls back. release relay 203 (or 302) is short-circuited. This results in the energization of the control magnet 219 (or 319) and the operation of the rewinding magnet 215<1> (or 345) over their respective off-normal contacts. In the two-motion selector, Fig. 3, the wipers fly round to an extreme position and drop back when the control magnet is energized. In the call-finder the relapse of the switching relay 72 causes the rewinding magnet 15 to operate until contact 25 releases the off-normal relay 56 and relay 64 falls back. If the calling party hangs up before the finder has reached his line, relay 64 pulls up over 85, 86, 91 and energizes the rewinding magnet.