Patent GB-171995-A (GB)
Title: Improvements in or relating to automatic switches for use in telephone or like systems
IPC: H01H67/16
Filed: 1921-11-14
Abstract: 171,995. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Richardson, R. G.). Nov. 23, 1920, [Convention date]. Automatic exchange systems.-The vertical and rotary ratchets of a modified Strowger switch, acting as a call-finder, are operated simultaneously. The wipers partake of the vertical movement, and on the completion of that movement are released from a rotary catch so as to fly round and catch up with the rotary controlling member. The two movements are controlled by auxiliary wipers 93, 94, the first of which partakes only of the vertical and the second of the rotary movement. The line and test wipers 90, 92, 91 are mounted on a sleeve 312, which rests on a pin 313 fixed in the main shaft 300, to which it is also connected by a spring 308, which keeps an arm 310 in engagement with a lug 309. The vertical ratchet 301 is in the form of a sleeve so that it need not turn with the shaft 300, and the rotary ratchet 302 is mounted on a fixed bracket 304 so that it does not rise with the shaft 300 but is able to turn the shaft by means of a rod 307. The sleeve 312 is at first prevented by a roller catch 321 from partaking of the rctary movement of the shaft 300, but as soon as the vertical movement is completed a magnet is energized to attract the armature 322, which releases the catch 321 and allows the spring 308 to rotate the sleeve 312 until the arm 310 engages again with the lug 309. A contact 54, 55 is closed by this action. Circuit arrangements. The upper winding of the relay 16 of a calling line is energized in series with relays 17, 18 corresponding to the tens and units digits of the calling subscriber's number. The relays 17, 18 belong to a set of 20 relays common to the 100 lines served by a group of finders, and they serve to disconnect ground from corresponding terminals of the rows engaged by the vertical and rotary control wipers 93, 94. The relay 16, which acts as a combined line and cut-off relay, is only sufficiently energized to pull up its armature 19, connecting its other winding to the test terminal 31. Relay 17 closes a starting-circuit 80 to energize the relay 43 of the finder F, or if this finder is already engaged the circuit is extended over the wire 81 to the next idle finder. Relay 43 closes circuits for energizing the vertical and rotary magnets 47, 48 over the control. wipers 93, 94 and these magnets operate in conjunction with their interrupter relays 49, 50 to step the finder shaft up and around simultaneously. When the vertical wiper 93 reaches the terminal from which ground was removed by the tens relay 17, a high-resistance relay 44, being no longer short-circuited over the wiper 93, becomes energized, opening the vertical magnet circuit, grounding the wiper 93, and energizing the trip magnet 52 to release the wipers from the rotary catch, and when the rotary wiper 94 reaches the terminal from which ground was removed by the units relay 18 a relay 45 becomes energized and disconnects the rotary magnet. By the joint action of relays 44, 45 a relay 42 is energized (but at this time without effect) and a circuit is closed through the upper winding of relay 41, test-wiper 91, and lower winding of relay 16. Relay 16 becomes fully energized, disconnecting the tens and units relays 17, 18, and relay 41 locks itself in series with relay 40, which connects the wipers 90, 92 to the trunk 96, 98. Relay 40 also disconnects relay 43, but before this relay can relapse a holding ground is supplied from the succeeding selector over the wire 97 to lock the relays 40, 16. When the calling subscriber disconnects himself the relay 40 is unlocked and completes a circuit over the rotary off-normal contact 53 for the release magnet 51. Preventing wrong connections due to simultaneous calls. If two subscribers, say XX29 and XX62, should call simultaneously the call finder would be brought to rest on the terminals of subscriber XX22. But in this case there is no circuit over the test wiper 91 for the energization of relay 41, and since the contact 65 is not short-circuited by contact 62 the energization of relay 42 opens the circuit of relay 45, which de-energizes relay 42, and in the interval between the relapse of these two relays a circuit 57, 64, 76 is closed to energize the rotary magnet 48, which resumes its operation to find the line XX29.