Patent GB-313200-A (GB)
Title: Improvements relating to telephone systems
IPC: G01S1/24
Filed: 1928-03-08
Abstract: 313,200. Siemens Bros. & Co., Ltd., Patterson, W. G., and Tees, J. E. March 8, 1928. Automatic exchange systems.-On release of a selector comprising a feeding bridge, e.g. a first coda selector, the release relay B relapses, but the restoration of the switch is prevented and a forward engaged marking continues until a further slow-release relay BA has also released. The relay B cannot be initially operated unless the switch is at normal, so that the switch may again be seized before it has homed, but dialtone is not sent until after B has operated. In the case of a normal selector, application of the impulse-sending signal to the register-controller would be held up. First-party release is normal but in a call to a manual board, the operator controls release. Delayed dialling alarms are provided. Seizure of first code selector and A-digit switches. Relay L operates on seizure over the calling loop, and earths the last lead c. Relay A operates over c2, unoperated off-normal contacts n3, k3, D(2), I, 12, k2, h2, earth. Release relay B operates over a1 and locks up to b6, over which relay MD also operates, and earth at b5 then energizes slow-release relay BA and dialling relay C(1) in parallel. Contact b1 puts a further earth on lead c. Magnet DM of the, " A "-digit finder is then energized over wiper p1 and its normal contact to step the switch forward, and stepping continues over busy contacts. When an idle switch is found, relay K operates in series with DM and stepping ceases. Relay A is now connected over k2, k3 over wipers a<1>, b<1>, to a loop in the A-digit selector, the impulse relay of which is connected over wiper pu and l1 in series with relay B. Setting up a connection. A dialling signal is now sent from the " A "-digit switch over wiper bl to the b wire. Relay L repeats the impulses to the A-digit switch over pu, relay B remaining energized. The first routing digit sent over wipers a<1>, b<1> impulses relay A, which repeats to magnet V and relay C(2) at a1 to step the code selector. Off-normal contact n<3> disconnects the dialling signal, and contact n<1> opens the circuit of C(1) so that C falls back at the end of the digit, releasing in turn relay A. The switch then hunts for an idle outlet, relay A being connected over rm to wiper C<1>, so that magnet R and relay A interact. When an idle junction is found, test relay H operates to earth at ba2 in series with A(1) and locks up. Wiper C<1> is busied at h1, and the impulsing loop is extended at h2, h3 to the junction over which the remaining digits are sent. Release of register-controller. After the last digit has been sent, earth is removed from wiper p<1> so that K releases and the " A "-digit finder homes over wiper h. Relay B remains held at b6. All trunks busy. The selector steps on to dead last contacts, shaft contacts s1, s2, s3 being operated. Test relay H operates and busy signal BS is sent back at e3. On hanging up, relays L, B, BA release in turn. Completion of connection and release. When the called subscribed answers, polarized relay D operates, releasing MD, so that relay DD pulls up and repeats the metering reversal over a, b. When the calling subscriber hangs up, relays L, B release in turn and the outgoing loop is opened at l2 to release succeeding switches, but nothing further happens until BA relapses, when H is released to remove earth from wiper C' and the switch is homed. If the switch is again seized before it has homed, L will operate, but relays A, B cannot energize until the shaft contacts are at normal. Release of call to manual operator. Since there is no battery reversal on the outgoing loop, relay MD is not released and when the calling subscriber hangs up, release of L operates relay MH to battery on the outgoing a wire, followed by energization of relay MHA. Relays B, BA are guarded at mha1, mha5, and DD operates over mha6. Battery is connected from mha4 to the incoming a wire. to repeat the holding signal. If the calling subscriber again comes on, relay L operates over its left-hand winding, releasing MH, MHA, and DD. When the operator clears, MH, MHA de-energize to release the switch. Delayed dialling. After a time interval, relays B, A are released from the register-controller, and relay M pulls up and locks: shortly after relay K is released from the controller and relays B, A then co-operate. Relay MD is released at m2 and relapses after B again pulls up, closing md4 to light an alarm lamp PG and close an alarm circuit. The finder switch cannot home until the selector is at normal as m7 is operated. If the subscriber now dials, the vertical magnet V is impulsed by relay A, which is energized in series with D(2), I, over 12, but since relay H is shorted at m6 and s1, the switch steps to its last contacts, when H operates, and NU tone is connected up at s3. When the calling loop is opened, the switch releases, and the finder switch homes.