GB494498A - Telegraph exchange system - Google Patents

Abstract

494,498. Telegraph exchange systems. LORENZ AKT.-GES., C. April 29, 1938, No. 12882. Convention date, May 7, 1937. [Class 40 (iii)] A long telegraph signal clears the connection by means of two successive slowly retracting relays, the first of which R is influenced by the telegraph signals of both directions of traftic, while the second L is governed by a contact r2 of the first and effects the release by its contacts l5, l7. The first relay has two windings RI, RII, which are affected by the signals. The winding RI carries current if no signalling is taking place in the outward direction, but is short-circuited on each reversal of a contact e by the signals. The winding RII receives current when the relay S is energized by received signals, but is short-circuited in the pauses. The effect of the windings RI, RII cancel each other. Thus the relay retracts if a long clearing signal is sent in either or both directions. To reduce the number of relays, the second relay L is also used to reverse, by its contacts l1, l2, the direction of the current in a system in which the connected printer motors Mo are started by a reversal of the direction of the current on the engagement of a selector. If, during dialling, the subscriber presses his clearing key, the calling key AT is automatically restored, the relay R falls back, and, by its contact r3 causes the relay T to fall back and release the preselectors and final selectors. That is, during this period the release is dependent entirely on the first relay R, and only after the response of the second relay L, through the closing of the contact s by the relay S, is the release of the second relay made dependent, by contact r2, l3, on the first relay, and the line release made dependent on the second relay. When the connection is released by one subscriber, an auxiliary relay U, which is in the circuit of a contact of the relay E in the other subscriber's line a1, b1, prevents re-engagement of the latter's preselector by the continued energization of his relay E until a contact m2 is opened.