Transceiver device for binary data signals to be transmitted in telephone switching systems, in particular in small PBX systems

摘要

In so-called small telephone PBX systems, binary data signals are transmitted in both directions between a central device (ZE) and the terminal devices (telephone sets (T1-Tn)) connected to it. For transmission of setting information for visual and/or acoustic indicator elements (A) present on the terminal devices, unipolar pulses, which differ from one another in both their pulse amplitude and in their time duration, are transmitted as binary values. For the information to be transmitted in the opposite direction (actuation of keys), a bipolar pulse and a pulse-free condition corresponding to the rest potential of the line serve as binary values. The transmission line is terminated at both ends with a transceiver transformer (Uz, Ut) which has, in addition to the line-side winding (Wz3, Wt3), a transmission winding (Wz2, Wt2) and a reception winding (Wz1, Wt1). Electronic switches (T1 or T2), of which one (T1) is connected directly in series and the other (T2) via a dropping resistor (R8) to the transmission winding (Wz2), which for its part is connected to the supply voltage, can in each case be effectively closed by an associated control unit (STz) in order to generate the unipolar pulses used as binary signals in one transmission direction. In order to generate a bipolar pulse, two electronic switches (T3, T4) are coupled with the transmission winding in such a way that, as a result of the successively performed short-time closure, currents from opposite directions pass through the transmission winding during the closure period. <IMAGE>