Patent GB-289296-A (GB)
Title: Improvements in remotely controlled line selecting or telephone systems
IPC: H01H67/06
Filed: 1926-11-19
Abstract: 289,296. Aldendorff, F. Nov. 19, 1926. Divided application. Automatic exchange systems and selectors.- In a call-finder system, each group has two or more allotting switches TF and the starting relay R1 pulls up one or more of its armatures to start as many finders as there are simultaneous calls. Detailed description is given of a system using tandem finders with two allotters per group in each stage. The finders, numerical selectors and one set of allotters are stop-controlled, and are driven by electric motors as shown in Fig. 1 and are provided with governors. Tandem call-finders, Fig. 2. When a single relay 20 pulls up, starting relay 28 pulls up its dotted armatures to energize the control magnets 11<1>, 112 of the finders LF1, LF2. If two line relays pull up at once, relay 28 pulls up all its armatures to start a second pair of finders (not shown) over the allotting switches TF3, TF4. Magnet 11<1> locks itself to the control wiper 42 and energizes relay 47 which marks the finder LF1 calling to the finders LF2. When the line is found, switching relay 45 shunts its high resistance winding by the low resistance upper winding of relay 47 to mark the line busy. Switching relay 130 in the second finder pulls up on the relapse of the control magnet over a front contact oi the group selector release relay 115 which was energized over an additional winding when the magnet 112 pulled up. Relay 130 short-circuits relay 47 to give control of relays 45, 23 to relay 115. Relays 47, 115 on first pulling up complete driving circuits for the allotting switches. The switch TF1 is of stepby-step type and the switch TF2 is like the binders. The relay 60 in the one case and the control magnet 117 in the other connect together the two test wipers 62, 65, and 121, 123 and the driving circuit is thus maintained if the first idle finder happens to be already appropriated by the other allotting switch over wiper 65 or 123 and a back contact of relay 60 or magnet 117 in such other switch. Group selector, Fig. 3. Line relay 135 removes a short circuit from release relay 115 before it has time to fall back. The first impulse of the digit energizes dialling relay 144 but not the control magnet 111'. At the end of the impulse however the magnet 111' is energized over 147, 150, 148, The motor is already energized in a circuit over 155 and the wipers therefore move to terminal 156. The beginning of the next impulse energizes this terminal whereupon the wipers move to terminal 158 which is energized at the end of the impulse, the wipers then going to 159. Subsequent impulses cause a similar series of double hops. The relapse of the dialling relay energizes relay 170 over off-normal springs 161 whereupon the switching relay 162 pulls up its dotted armatures connecting the control magnet to the test wiper 151 and short circuiting relay 170 which however holds up over its left-hand winding and a front contact of the control magnet until an idle line is found when it falls back and bridges the talking wipers to operate the line and release relays 203, 204 in the connector. Relay 204 energizes the upper winding of relay 162 which pulls up its remaining armatures switching the line through and cutting off the line relay 135 whereupon relay 115 falls back, the connection however being held at 175<1>. To prevent false operation, relay 162 (upper) is short-circuited while the control magnet is energized. Connector. Dialling relay 209 pulls up at the beginning of the first impulse and at the end of the impulse the switch moves to 220, subsequent impulses of the tens digit causing a series of double hops as in the group selector. At the end of the digit relay 209 energizes relay 226 which locks up, connects the control magnet to wiper 216 and connects the impulse wire 232 to a relay 234 which therefore' pulls up at the first units impulse over its lower winding in series with the control magnet, short-circuits this winding to energize the' control magnet and holds over its upper winding until the end of the impulse. The wipers move to the next terminal which, being connected to 246 is dead until the next impulse begins whereupon the wipers take another step relay 234 remaining unaffected by this and subsequent even impulses. Subsequent odd impulses operate relay 234 in the same way as the first. Busy signal. Relay 253, energized by relay 234, locks itself and prepares the test circuit which is completed on the relapse of dialling relay 209. If the line is busy, relay 254 is unable to pull up and busy tone goes back from 263 over a third winding 299 acting inductivelv on the line relay. Ringing current. If the line is idle. relay 254 starts a. ringing interrupter- 269 which projects alternate battery and grounded ringing current over the upper wire. When the called party replies, relay 2'i6 cuts off the ringing current, completes the connection, releases relays 226, 253, and subsequently acts as the back-bridge relay. Release. When either party hangs up, relay 203 is short-circuited either by the relapse of the line relay or over 282, 285, 283, starts the motor, energizes the control magnet and releases relays 254 and 162, Fig. 3. Relay 162 energizes the control magnet which starts the motor and releases the wipers. Relay 170 pulls up during the restoration and causes relay 162 to hold its dotted armatures. When the selector is restored however the relay is released and releases the finder switching relays and the cut-off relays. The finders have no normal position.