Patent GB-289049-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/30
Filed: 1928-04-04
Abstract: 289,049. Associated Telephone & Telegraph Co., (Assignees of Nelson. M. D.). April 22, 1927, [Convention date]. Automatic and semi-automatic exchange systems.-Routine testing equipment for use with connectors is adapted to subject each connector to a cycle of tests during which it simulates the various conditions and functions of calling and called lines. If desired, a single group of connectors may be tested, or a single connector may be tested repeatedly. The test equipment may wait for a busy connector to become free, or it may skip busy connectors. When a fault is found, the test is stopped and a lamp is lighted to indicate the nature of the fault. Lamps are provided to indicate the connector under test at any time. Cycle of tests for a single connector. Operation of key 41 or 42 connects earth to wire 13 by way of wire 33, and relays 20, 5, 10 energize. Line relay 405 of the connector under test is connected in a calling loop through relay 109, which locks, short circuits its upper winding and disconnects fault lamp 1 from the fault circuit 262. Relay 122 energizes over the earthed test wire 3 and disconnects signal lamp 2 from circuit 262. Relay 113 energizes and connects up relay 241 at the next closure of cam springs 211 which are operated periodically, while when these springs open, relay 238 energizes and extends the line wires 1, 2 over series resistance 216 to impulse springs 215. The digits 99 are sent into the connector, the impulse series being terminated by the closure of short-circuiting springs 213, and relay 238 is disconnected by the energization of relay 245 over springs 211. The line and test wires 1', 2', 3<1> corresponding to this number are connected respectively to ring test relay 329 and relay 100 over front contacts of a group relay such as 38, 39 described below. The number 99 normally gives access to a test clerk's position. If the connector responds correctly, and the test wire 3<1> is earthed, relay 100 energizes, disconnects fault lamp 3, and connects the calling line wires 1, 2 to polarized relay 147 (lower), which energizes and connects up relay 141. Relay 300 operates and fault lamp 4 is disconned. Ring. ing takes place at the connector, and relay 329 responds, and the first ringing period causes relays 314, 309 to energize, disconnecting fault lamp 5 and relay 300, and bridging line wires 1'. 2<1> through high resistances 331, 332. When sluggish relay 300 relapses, resistance 331 is short-circuited to represent the reply of the called party, and ring cut-off relay 420 energizes. Backbridge relay 400 reverses the current over the calling line wires 1, 2 and polarized relay 147 falls back. If ring cut-off relay 420 pulls up prematurely before relay 300 has relapsed, relay 147 on falling back closes a holding circuit for relay 300, and fault lamp 6 lights in due course. If ring cut-off relay 420 does not cut off the ring- ing current, a second period causes the operation of relays 303, 305 and fault lamp 7 is connected up. Polarized relay 147 on falling back disconnects fault lamp 8 and connects up relay 320, which extends the called line wires 1'. 2<1> to polarized relay 317 (lower). If the line wipers are reversed, this relay does not operate and fault lamp 8 becomes lighted. Relay 317 on operation extends line wires 1<1>. 2<1> to a source of tone current 335 which is transmitted through the connector and an amplifier 130 to operate a voice-current relay 131. Relay 134 (energized over start key 41<1>) releases, and relays 136 106 energize, disconnecting fault lamp 10, Relay 106 opens the calling loop to simulate release by the calling party. Relay 430 energizes momentarily until release relay 410 falls back. so that earth is removed from the test wire 3 for a short period. Relay 122 relapses, connects up relay 116 which locks and cuts out fault lamp 11 and disconnects sluggish relay 113. When earth is replaced on the test wire 3, relay 122 re-energizes, disconnecting signal lamp 12 and connecting up relay 324 which opens the called line loop to release the connector, and relays 228. 232 pull up and lock. releasing relays 309, 314, 136, 141, 320. Relay 228 extends the test wire 3<1> to earth over relay 122 and wire 13 to simulate a busy line, and switches over the fault circuit from wire 262 to wire 262'. Sluggish relays 136, 106 relapse in turn and disconnect relay 324, and relay 228 disconnects sluggish relay 100, which on release completes the calling loop over wires 1, 2 to initiate a fresh call. Relays 122, 113 energize as before and the digits 99 are sent into the connector with shunt resistance 217 across the line (relays 232, 238 being energized). Relay 249 energizes over springs 211 and disconnects relay 238. The called line being marked busy, busy relay 425 pulls up in series with relay 152, which locks, disconnects fault lamp 13 from circuit 262<1> and extends both line wires 1, 2 to the amplifier 130. Busy tone is now connected up at the connector and is amplified to operate relay 131, which connects, up relay 136 to cut out fault lamp and relays 106. 324 to release the connector. Relay 126 now energizes and removes earth from holding wire 13, and all the relays locked thereto are released. Relays 20, 5. 10 fall back in turn. Connector to be tested engaged. Relay 15 energizes over the test wire 3 and connects earth to wire 29 instead of wire 33 to energize relays 226. 220, 224. Magnet 205 operates in parallel with relay 224 and effects the closure of cam springs 208, 209 after regular intervals. Magnet 202 of the switch 200 then operates in parallel with relay 260, which disconnects magnet 205 and relay 224, and. the latter in turn disconnects magnet 202. This interaction continues until, if the connector does not become idle, relay 257 energizes, disconnects magnet 205 and lights busy lamp 17 over wire 19. An alarm 37 is sounded if key 43 is operated. The switch 200 is restored by releasing key 41 or 42, when relays 226, 200 fall back. If on the other hand, the connector becomes idle, relay 15 falls back, and the test cycle is started. Relays 226, 200, 224 fall back and the switch 200 is restored. In a consecutive test however it may be desired to skip busy connectors, and this is offected by means of key 70 as described below. Fault signals. Magnet 205 is energized throughout a test cycle over wire 13, and controls relay 253. Accordingly, if any test fails, the test is stopped and the corresponding fault lamp is lighted after an interval by the connection of earth to wire 262 or 262'. The alarm 37 is sounded if key 43 is operated. Arrangements of distributors and test keys. The test equipment is connected to the connectors by means of 25-point primary and secondary distributor switches, and each switch frame of 25 connectors is divided into two groups numbered 1-12 and 13-23, a group relay such as 38. 39 being provided for each group. The connector under test at any time is indicated by a group lamp (shown in a dotted circle) and a switch lamp (shown in a double dotted circle). For a consecutive test of all the connectors, keys 41, 43 are operated, and the test may be started at any particular connector by operating the magnets 35, 36 of the distributors by means of stepping keys 45, 46. After the first connector has been tested and earth is removed from holding wire 13 by relay 126, relay 20 falls back followed by relay 5, and an impulse is sent to magnet 36 to step the secondary distributor into engagement with the next connector. To skip busy connectors, key 70 is operated to connect a resistance 65 in series with relay 15, which then energizes partially over an earthed test wire 3 and attracts armature 17. Relay 5 energizes and sends an impulse to magnet 36, relay 20 being disconnected. Missing connectors are represented in the test banks of the secondary distributors by earth through a high resistance, which causes partial energization of relay 15 in a similar manner. Relay 30 energizes in the 25th position of a secondary distributor, and when relay 20 falls hack, an impulse is sent to magnet 35 to advance the primary distributor. In the case of an unused secondary distributor, relay 30 energizes in series with relay 15 which energizes partially, and the primary distributor is advanced. When all the connectors have been tested, two-step relay 27 energizes over contacts of the last group relay 40, lighting lamp 16 and operating audible sional 37. To test a single group of connectors only, keys 42, 43 are operated, as well as stepping keys 45, 46, and as the end of the test, relay 27 energizes over key 42 and contacts of the group relay. If only key 41 is operated, the same connector is tested repeatedly. Key 44 serves to release the test equipment when a fault has been found.