Patent GB-256697-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1925-05-13
Abstract: 256,697. Siemens Bros. &. Co., Ltd., and Patterson, W. G. May 13, 1925. Automatic and semi-automatic exchange systems.-At a first selector having a feed bridge, a polarized relay D responds to reversal of line current upon the reply of the called party and connects up delayed metering equipment of the kind described in Specification 200,928. A busy condition at any stage of the connection is signalled back by intermittent reversals of line current, and a relay LF becomes energized in this case' to prevent metering and send back a busy signal. Release of the succeeding switches, and if desired of the first selector itself, takes place after a prescribed interval. The invention is described with reference to a first code selector in a system employing register-controllers of the code-translating type, the selector having access over a finder switch to an " A " digit switch. The line switch is of the kind described in Specification 241,655 which, when released at a selector while the calling line is still bridged, moves to last contacts, over which a tone signal is sent. The connector is of the kind in which the answering and feed relay energizes and reverses the line current on the reply of the called party, and is energized intermittently if the called line is busy under control of the ring cut-off relay, which also serves as a busy relay. Normal operation. Line relay L upon energization connects up release relay B, places a preliminary ground on the test wire at contact l3, and closes a circuit for impulse relay A over relay D (2) and off-normal contact n13, which is subsequently shunted by contact c2. Relay A connects up change-over relay C (1) over contact n1, and relay B connects up relay D (1), which is however inoperative. The test wire is now grounded at contacts b1 and c6. Magnet DM is connected over contacts m7, k6, c3, k1 to wiper C<1>, the normal terminal of which is grounded over contacts c4, m6, b4. The finder rotates until an idle " A " digit switch is found, when test relay K is no longer short-circuited, and energizes and locks over wiper C<1>. Impulse relay A is connected at contacts k2. k3 to wipers A', B<1>. and release relav B is connected at contact k1 over wiper P<1> to the impulse relay in the " A " digit switch. A dialling signal is transmitted over wiper B<1> and the b wire. Dialled impulses are repeated at contact l1 to the impulse relay in the " A " digit switch, and when the exchange code has been sent, impulse relay A receives the first train of translated impulses, which are repeated to the vertical magnet VM and series relay C (2), which falls back at the end of the train and transfers the circuit to the rotary magnet RM, Relay A also falls back, contact n3 being open. The rotary magnet RM interacts with relay A to find an idle outlet, relay A being connected to test wiper C‹ at contact rm over contacts h1, m5. When an idle outlet is found, relay H, which was previously short-circuited, energizes in series with relay A, which is now inoperative, and locks at contact h4. At contacts h2, h3 wipers A', B<1> are connected to wipers A‹, B‹, so that the remaining trains of impulses are sent directly to the succeeding switches while at contact h1 the test wire is extended to test wiper C‹. Relay K is released when all the impulses have been sent ,and switches through the talking wires. Winding D (2) is connected up, and the reversal of current at the connector when the called party replies causes polarized relay D to operate. Relays J, JA were connected up by the energization of relay C, and relay D opens the. locking circuit of relay J, while at contact d1 ground is connected to relay DA (1), which operates when battery is applied to wire 10, and locks over winding DA (2). Battery is subsequently applied to wire 11, and relay DB (1) energizes in series with winding DA (3), locks over winding DB (2) and closes the metering circuit m. Relay DA falls back when this battery is removed, and releases JA, thus preventing further metering. If the calling subscriber attempts to clear before metering has taken place, relay B is held at contact da3. Called line busv. Intermittent reversal of line current is applied at the connector, and polarized relay D responds. Relay J is released as before, and on the first relapse of relay D, a circuit is closed at contact d4 for relay LF, which locks at contact lf1. The locking circuit of relay DA (2) is opened at contact d2. Impedances I are inserted in the line wires to reduce clicks due to current reversals, or, if desired, an absolute break may be arranged. At contact lf5 is connected up relay EA of a pair EA, EB forming part of a delay device similar to that including relays DA, DB. The purpose of this is to avoid possible release due to a current reversal caused bv awkward removal of the receiver by the called party. In this case, relay LF would operate in response to the reversal, but relay EB would be disconnected by relay DA a little later. A busy signal is sent from wire NU over contacts lf4, d3, eb3 and the a wire, being rendered intermittent by the operation of contact d3. When relay EB operates, the ordinary busy signal is sent from wire BB. If only the succeeding switches are to be released, contact eb7 is omitted. Relay D is released when relay EB operates, while holding ground is disconnected from test wiper C<0>. When the calling party hangs up, relays L, B, H relapse in turn, so that ground is removed from the test wire. The release magnet MM operates and restores the selector, the opening of contacts mm preventing energization of relay B meanwhile. The restoring circuit for magnet DM is closed at contact h6. If the first code selector is to be released, contacts eb4, eb5, eb6 are omitted. Operation of relay EB now at contact eb7 disconnects relay H, which opens the test wire, so that the line switch moves to last contacts over which the busy signal is continued. Line relay L is disconnected and the selector releases. All outlets busy. In the 11th rotary position, shaft contacts s1, s2, s3 are operated. Test relay H is no longer short-circuited and energizes in series with relay A and locks. A busy signal BB is sent over contact s3 and the a wire. Relay J remains locked since relay D has not operated, so that relay LF does not energize. Release takes place when the calling party hangs up. Call to manual position. Battery is connected back from the operator's cord circuit to wiper A<0>. When the calling party clears, line relay L falls back, and relay MH energizes over wiper A<0>, closing a fresh circuit for release relay B to hold up the connection until the operator clears. Clearing before a register-controller has been seized. Relays A, C are energized at this time, but not relay K. Line relay L falls back and releases relay A. which closes a circuit over contacts k5, b3, cl, h5 for relay M, which locks and disconnects magnet DM at contact m7. At the same time, the vertical magnet VM operates in series with relay C (2). Release relay B relapses after an interval, and disconnects relay M, which completes the restoring circuit for magnet DM at contact m<7>, relay C having meanwhile fallen back. The, release magnet MM returns the selector to normal. Premature dialling. Impulses are repeated to impulse relay A at contact l2, and since relay K is not operated, relay M energizes at the first impulse, locking and disconnecting magnet DM. Change-over takes place in the usual way, but since test relay H is permanently short-circuited at contacts m5, m6, the selector moves to the 11th rotary position, in which a continuous tone NU is sent back over the a. wire.