Patent GB-307538-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1927-12-09
Abstract: 307,538. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. Dec. 9, 1927. Semi-automatic exchange systems.-In manualto-automatic calls, the A-operator on plugging in obtains connection to an idle junction over which the speaking connection is to be set up. A hunting switch at the incoming end of the junction immediately finds an idle sender which is then connected by a further shunting switch to a B- operators' position. The B-operator is informed by a lamp that she is required and the A-operator by tone that she is connected up and the latter immediately gives the B-operator the number to be set up. The B-operator has speaking connection to the calling subscriber until she has completely set up the number. If two keys are pressed simultaneously or without sufficient interval an alarm is given and the operator restores the sender and sets up the number again Premature release is described. When an A-operator plugs into jack 10, relay L operates to connect earth at 18 to the top of relay K. If SF is on a busy sender, K is shorted over wiper 17 and magnet DM1 operates to step SF. When an idle sender is found, K operates and relay A of the sender, Fig. 3, energizes overwiper 17. Relay H operates over its upper winding so that earth at 33 operates stepping relay K when PF finds an idle B-operator's position. Relay AP, Fig. 5, at the B-operator's position thereupon pulls up in series with the lower winding of relay H over wiper 30, relay TD being operated in series with the B-operator's transmitter, and relay KK operates and locks up to 39. Relay AP lights lamp 41 to call the B- operator. A tone is connected from conductor 42 to the A-operator in two periods, one until slow-relay TA operates, and the second after slow-relay TB has energized until TA de-energizes, after which a transmission loop is formed between the operators, and the required number communicated to the B-operator. Setting up digits. Operation of any one key Fig. 5 connects relays AB, MR in series with one or two of wipers 64, 65, 114, 107 in parallel. Relay AB operates and energizes relay TC which locks up to the storage-set release key 73 and disconnects the B-operator from the transmission loop. Over the first two wipers, relays XA, WA operate to connect earth to conductors 85, 86, while the latter wipers connect earth direct to conductors 115, 108. In this way, one or two relays of the first storage-relay set MAV - - MZ energize in series with relay DC and lock up over conductor 93. Relay DC energizes relay SD so that when DC restores on the key being released relay MS operates partially in series with SD, and locks over 93 releasing SD and switching the impulse conductors to relay set CW - - CZ. Depression of four keys in turn sets all the relay sets, relays CS, DS, US operating after the further digits to extend the impulse conductors, so that earth is connected over conductor 99 to prepare the required stop circuits in the contact banks of wipers 131, 146 of SS. A resistance 71 is arranged to preserve the marginal balance of relay MR when only one relay is operated by a key. Key sender alarms. If two keys are depressed simultaneously, three parallel circuits are formed in series with relays MR, AB instead of two. so that marginal relay MR operates to energize relay AL and so light lamp 75. Relay AB is energized during depression of a key. and partiallv operates relay TS, which pulls up completely when the key is released to cut the circuit of slow-release relay SP; SP releases TS but if the interval between digits is too short, AB again operates before TS releases, and relay AL is operated. On seeing lamp 75, operator throws key 73 to operate relay CA, Fig. 3, and so release the register sets. Specification 303,921 is referred to. Setting, up connection. Impulsing is begun by depressing start-key 36, Fig. 5, to short relay H, Fig. 3; this could be done automatically if the holding circuit of H included a back contact of relay US, Fig. 4. Relay K1 is thereby released to disconnect the B-operator, and to operate relay S, Fig. 2, from armature 39 over wiper 16. Relays S locks up and relay K is now held from earth at 39. Relay K1 disconnects ST, but until the latter releases, relay SZ, Fig. 5. operates from earth at 39 over 128 - - 131. The pendulum vibrator magnet V. Fig. 3, is thereby energized to start impulsing to magnet DM3 of SS over 135 and to the outgoing trunk 138, 139, Fig. 2, over contacts of relay MA operated by MS. Fig. 4, at 137. When wiper 131 of SS reaches the contact earthed from 98, Fig. 4, relay SZ operates to stop impulsing and is locked up by relay SA operated over wiper 141. SS is now self-stepped over wiper 141 to the 13th contact, when SA, SZ release in turn and impulsing again continues until the stopping circuit from 97, Fig. 4, re-energizes SZ. Wipers 131, 141 of SS are now stepped off the banks and wipers 146. 147 come into action, the last two digits being similarly transmitted. When SS returns to normal, relay CO, Fig. 3, operates over 142, 143 before SA, SZ release, so that relays K, A release in turn. The speaking circuit is connected up over armatures 59, 126, and 10, 127 and the storage relays are released at 91. Premature release. If the call is abandoned during setting up of the connection, release of relay A restores the storage relays and at contact 158 forms a homing circuit for SS over wipers 141, 147, the non-commoned contacts thereof being earthed from the storage relays. Relay SA is operated meanwhile to busy the sender over 39, 150, 24, 23 to a wiper 17 of SF. Supervisory signals. Polarized relay D, Fig. 2, operates over the called loop before reply to disconnect battery over 151 from the calling loop so that the A-operator's supervisory lamp is lighted. On reply, reversal of current releases D to disconnect the lamp. If however the wanted subscriber is busy, busy flash intermittently operates D to flash the operator's lamp.