Patent GB-260356-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/22
Filed: 1925-07-30
Abstract: 260,356. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. July 30, 1925. Semi-automatic exchange systems. - Routine testing equipment is provided for use with callindicator systems of the type described in Specifications 229,371 and 223,792. When a test is to be made, the operator removes her head-set plug from the normal jack, thereby busying her position, and inserts it in a special jack J1. The test equipment is connected over a switch TRS to one of the trunk relay groups, and code impulses are sent from a switch SS to set up a particular number on the display lamps. The plug of the first cord circuit is inserted in a test jack J2, and ring-back tone is heard. The supervisory arrangements associated with the cord circuit are then tested. The same series of tests are made with each cord circuit, and preferably, as each plug is withdrawn, the switch TRS is advanced to connect up the next trunk relay group, and a control switch CS is advanced to set up a fresh number on the display lamps, so that all the lamps may be tested. Circuit arrangements. When the operator plugs into jack Jl, relay 1 energizes. If the test equipment is in use, relay 13 is operated, and busy tone BT is connected up. If it is free, relay 4 energizes, locks and connects the equipment to the switch TRS. Relay 13 energizes, and vibrating relay 18 which short-circuits itself at intervals is also connected up. Wires 39, 40 leading to a trunk relay group are now extended to relay 24, which energizes and connects up sluggish relay 26. When the relay group is connected to the decoder, wires 39, 40, which were previously connected to battery and earth, are looped, so that relays 24, 26 relapse, sending an impulse over wiper 31 to magnet 28 to initiate stepping of the switch SS, which is continued under the control of vibrating relay 18. The terminals of the sending switch SS are connected through the control switch CS to battery through a resistance 41 or 42 in accordance with the code system, so that code impulses are sent over wires 39, 40 to the decoder as the switch SS advances to set the number 1111 on the display lamps. In its last position, wiper 31 is connected to the upper winding of relay 43, which energizes, locks over its lower winding and short-circuits its upper winding to allow magnet 28 to operate and move the switch SS to normal. Relay 43 connects wires 39, 40 to the right winding of polarized relay 21. The operator inserts the plug of the first cord circuit in jack J2. Sleeve relay 46 connects the headset to wires 39, 40 at contacts 47, 48. The trunk finder associated with the cord circuit hunts for the trunk relay group in the usual manner, and ringing current is sent over jack J2 and A.C. relay 50, which responds and connects up relay 53, causing magnet 57 to advance the switch TS one step far each ringing period. The operator receives ring back tone in the usual way over wires 39, 40. In the 3rd position of switch TS, relay 59 energizes, disconnects relay 50 and directly loops the jack springs to simulate the reply of the called party through induction coil IC, over which a hightone HT is sent. Interruptor 63 is connected to relay 53 to advance the switch TS a further step, whereupon relay 64 energizes and switches the operator's headset over to the cord circuit through jack J2. The operator removes the plug from jack J2, releasing sleeve relay 46, which advances the switch TS. Since relay 21 is still bridged across wires 39, 40 to represent a calling party, the " wrong disconnect " signal is given. The plug is re-inserted, re-ringing takes place, and the switch TS is advanced again, and in the 7th position, relays 59, 70 energize, and the former loops the jack springs as before. This effects a reversal of current in the cord circuit which energizes polarized relay 21, and connects up a low-tone LT to indicate that the metering condition has been set up. Interrupter 63 controls relay 53 to advance the switch TS two steps. Relay 73 now energizes, locks and disconnects relay 21 to simulate release by the calling party, causing the clearing lamp to light. Interrupter 63 advances the switch TS, and in the 10th position magnet 81 operates and moves the switch TRS into engagement with the next trunk relay group. The test terminals of this switch are normally dead, but any relay groups not equipped are marked by ground, by which a local circuit is completed for advancing to the next relay group. At the next step, relay 59 energizes and loops the jack springs to operate the flashing signal. The operator removes the plug from jack J2, releasing relays 46, 73, 43, and since relay 73 is slow to relapse, an impulse is sent to magnet 80 to advance the control switch CS one step, in preparation for sending impulses corresponding to the number 2222. Relay 24 energizes over the wires leading to the second trunk relay group, and the operator makes a series of tests with the second cord circuit. One or more cord circuits may be employed a second time if necessary. If it is desired to employ the same trunk relay group with each cord circuit, an additional jack similar to J2 is provided, the corresponding sleeve relay opening the circuit of magnet 81 as well as performing similar functions to relay 46. Wires 84, 85 extend to a jack over which a hand set may be connected in parallel with the head set, relay 86 being operated.