GB442192A - Improvements in or relating to double current telegraph installations - Google Patents

Abstract

442,192. Code telegraphy. NATIONALE TELEPHON - UND TELEGRAPHENWERKE GES., 136, Mainzerlandstrasse, Frankfort-on-Main, Germany. May 10, 1935, No. 13839. Convention date, May 19, 1934. [Class 40 (iii)] Relates to double-current telegraphy in which the spacing battery at the sending end is strong enough to reverse the line current by overpowering the marking battery at the receiving end during a spacing impulse. According to the invention the receiving relay is provided with a supplementary winding so connected in relation to the batteries that it eliminates the effect of bias when the receiver is used for monitoring at the sending end. During the transmission of a five-impulse character by station A the contact u is closed. If the transmitter makes contact at S, marking current goes from marking battery Br1 through the line, and through battery Br1<1> and sending- on relay Ea at the repeater station U, so that armature ea remains in the marking position as shown. When the transmitter breaks contact at S, however, the spacing battery Bal becomes effective and overpowers the repeater battery Br1<1> causing armature ea to connect battery Bu to line Lb and so to send on a signal to station B. The battery power has to be adjusted so as to compensate for line losses, and as a result the spacing signals are stronger than marking signals in coil l of the receiver at the sending end. In order therefore that this receiver may serve for monitoring purposes, a supplementary coil g is provided to neutralize this bias. The current strengths are adjusted by means of resistances Ra1 Rg1, Wa, Ru and the adjustments of Ra1 Rg1 may be coupled. The transmitters may have make-before-break switches K as has been shown in the case of station B, the cam switch V being of the kind described in Specification 389,999. Specification 442,278 also is referred to.