Patent GB-370424-A (GB)
Title: Circuit arrangement for printing telegraph systems
IPC: H04L12/12
Filed: 1931-01-06
Abstract: 370,424. Telegraph exchange systems. LORENZ AKT.-GES. C., 1, Lorenzweg, Tempelhof, Berlin. Jan. 6, 1931, No. 523. Convention date, Jan. 8, 1930. [Class 40 (iii).] In a telegraph manual exchange system, a calling signal, comprising an interruption which may be brief, starts the printer motor ; and a clearing signal, comprising a long interruption, stops it. Idle state. Normally a circuit is closed through the magnet R associated with the jack FK, through the armature r1, line ab, magnet I at subscriber's station, and central calling battery B, so that magnets I, R are both energized, while the line magnet E and transmitter S are short-circuited at 1112. Calling exchange. The calling subscriber A breaks the line circuit at AT, whereupon magnet I releases and at i connects magnet III to the a.c. source G, so that the local printer motor M is cut in at 1112. Contact at 1112 holds the relay I inactive, puts the calling switch AT out of action, and cuts in the receiver E and transmitter S. The jack magnet R releases also, lighting the calling lamp at r2. The operator inserts plug AS into jack FK, and so (1) re-energizes relay R by connecting it via sleeve c<1> to battery W1, the calling lamp being thus extinguished; and (2) energizes relay N in a circuit which includes the battery B, line ab, subscriber's station, and the operator's own transmitter S and receiver E, the switch Abfr having been changed over when the plug was inserted. Relay V is thus energized by removal of the short-circuit n ; and relay Z is energized by removal of the short-circuit v1. The circuits of N, V, Z are so arranged that these relays hold on throughout the connection. Calling subscriber. The exchange operator then inserts plug VS into the jack of the called subscriber, whose calling-lamp relay R (not shown) is held on in a circuit which includes the slow-acting relay U, which connects the line through at u1. The magnet I at the called station is released during the momentary interruption of the line which occurs while relay U is pulling up. Message signalling. Current is supplied by the central battery B via plug tip a1 to the through circuit which includes line a, b, calling subscriber, Fig. 1, plug ring b1, relay N, plug tip a11, called subscriber, plug ring b11 and earth via v3. The receiver line magnet E at each subscriber's station, Fig. 1, intermittently closes the contact e for brief periods and so operates the clearing clutch magnet K, but the clearing device is restored to normal, before it can become effective, at each interruption of the contact e. Throughout the message the magnets III, R, Z, V, U, N remain energized while magnet I is de-energized. Clearing. The clearing signal is given by means of a prolonged interruption of the line circuit SLT, whereupon at each subscriber's station magnet E releases and cuts in at e a clutch magnet K which connects to a constantly rotating shaft a contact breaker which, after a brief interval, breaks the contact k, whereupon relay III releases, cuts out the motor M at III1, short-circuits the apparatus E, S, SLT at III2, and removes the shortcircuit from relay I. At the exchange, relay N releases when the line is broken by the clearing signal and short-circuits relay V at n, the clearing lamp SL being thus cut in at v2. When plug AS is pulled battery B is applied to the circuit of subscriber A, including relays E, I; and when plug VS is pulled a similar result follows at the other subscriber's station, relays Z, U releasing also. The clutch for operating the contact k preferably comprises a constantly rotating armature adapted to drive a normal stationary part which carries the electromagnet. When the electromagnet is energized the part carrying it is rotated, and when it is de-energized the part is released and restored by a spring or gravity. When the part is moved through a sufficient angle it closes contact R. Modifications. In one modification, Fig. 3 (not shown), the clearing clutch K at the subscriber's station is dispensed with. Magnet I is energized during a message as well as when the line is idle, and both calling and clearing are effected by temporary de-energization of this magnet. In a further modification, Fig. 4 (not shown), a single multiple-contact relay at the subscriber's station cuts in the motor M when de-energized by the call signal. During a message the relay is short-circuited by one of its own contacts, but it is mechanically reset, so as to re-establish idle conditions, when a particular type-lever (e.g. one operated by a group of zero impulses) is selected. Instead of D.C. impulses, A.C. impulses may be used for the message signals, the current being derived from the mains or from the motor M, which may be a motor alternator or a rotary converter. In this case the D.C. relays may be replaced by A.C. relays, or the A.C. may be rectified with copper-oxide rectifiers before being applied to the relays.