| 摘要 |
<p>608,856. Loud-speaking telephone systems. AUTOPHON AKT.-GES. March 8, 1945, No. 5805. Convention date, Dec. 4, 1942. [Class 40 (iv)] [Also in Group XXXVIII] A bridge rectifier network, arranged to supply current to one device independent of the polarity of the input current, has other devices connected across some of the rectifiers, so as to receive current whose magnitude depends on the input polarity. The invention is applied to a loud-speaking telephone substation, Fig. 2, whose speaking direction is controlled, as described in Specification 608,850, according to the polarity of current received from the exchange over the phantom of the subscriber's line. The relay E, which energizes the substation amplifier, is initially operated by a pulse of A.C. over condenser CI and remains operated thereafter over its own contact by incoming D.C. irrespective of the polarity thereof. The visual signal SZ and the relay U, however, are only energized when the incoming current is negative, U switching the amplifier into the " receive " position. Relapse of U on receipt of positive polarity switches the amplifier to the " transmit position. If the subscribers prefer to use the car-piece T, switch TK is operated, disconnecting U and SZ and also resistance W3 so that the D.C. current is reduced to operate switching means at the exchange, whereby weak A.C. is sent to the distant subscriber to cause his lamp SZ to glow. Clearing down is effected by opening switch ES which breaks the holding circuit for E.</p> |
