Patent GB-274143-A (GB)
Title: Improvements in electromechanically controlled switches and remote control signalling and telephone systems
IPC: H04Q3/00
Filed: 1926-01-19
Abstract: 274,143. Aldendorff, F. Jan. 19, 1926. Automatic exchange systems and selectors.-A stop controlled call-finder failing to stop on the calling line is stopped temporarily in its normal position in which the wiper shaft closes contacts in the circuit of the re-winding magnet, these contacts being opened when the spring is rewound to a predetermined degree, and at some point before the spring is fully re-wound the wipers are again released and the switch makes a second attempt at a reduced speed. If the finder fails to extend the connection, a timing switch which also controls the application of ringing current to a called line, causes the allotting switch to select a new one. In the system described the finders are associated with single motion connectors with two sets of wipers. Construction of switches. The wiper shaft 1 is started and stopped on a calling line by a magnet 12 and is driven, under control of a centrifugal brake with an adjustable collar 31 for varying the effective tension of the springs, by a spring barrel 8. After use, or if the switch fails to stop on the line, a pin 19 on the stopping disc engages a bar 18 to stop the wipers and a projection 22 on the off-normal cam closes springs 23, 24 in the re-winding circuit. On the first re-winding step, the spring barrel closes springs 21 to make the re-winding circuit independent of springs 23, 24 and at some later stage a projection 26 on the spring barrel engages a lever 25 carrying the spring 23, forcing the latter downward out of contact with spring 24 and subsequently allowing it to resume the position shown. Before the spring is fully re-wound, a member 9 shifts the bar 18 out of engagement with the pin 19 and if the magnet 12 is still energized the wipers fly round again. Call finder, Fig. 2. The line relay 40 energizes a common relay 64 and a relay 44 in a preselected finder whereupon the control magnet 12 releases the wipers which fly round until wiper 48 engages the calling terminal which is dead. Switching relay 47 then pulls up in series with the cut-off relay 54 and line relay 101 and release relay 102 of the connector pull up and cause the allotting switch TF to move on. Relay 64 energizes in a slow acting self-interrupting circuit a relay 107 which thus delivers slow impulses to the stepping magnet 112 of a switch SS which on reaching terminal 117 energizes a relay 65 which locks up. If the switch reaches 119 (or 120) therefore, an impulse is sent to drive the allotting switch on. If the call finder is successful however, relays 40, 64 fall back, and relay 65 is unlocked. If the call finder misses the line at the first attempt it is stopped in its normal position as described above and closes springs 23, 24 to put the re-winding magnet 11 in series with a relay 81. The latter short circuits itself allowing magnet 11 to pull up. Magnet 11 and relay 81 continue to interact, the circuit being maintained at springs 21 (closed on the first rewinding step), until the spring is fully re-wound. Before t'his stage however the wipers are released as described above to make a. second attempt. Connector. The tens digit which must be either 1 or 2 is repeated to magnet M3. If it is 1, the relapse of dialling relay 132 energizes wiper-changing relay 136 over spring 134 which is closed only wthen the wipers have made a single step. If it is 2 the relapse of relay 132 is without effect. The magnet M3 then responds to the units digit. Ringing current. If the line is idle, relay 150 connects up ringing current from the wipers 113, 114 of switch SS which is now being driven in a circuit 107, 130, 101. In the silent intervals wiper 115 connects negative battery to the lower winding of the ringing cut-off and back-bridge relay 161 which completes the connection when the called party replies and energizes a backrelease relay 163 which locks up and stops the switch SS. Release. When. either party hangs up, the connector is stepped on to normal either in a circuit M3, 171, 173, 81, (82) or a circuit M3, 190, 173, 81 (82). When the calling party hangs up, the finder flies round to normal where the spring is re-wound as described above.