Party Line Data Transmission by Balanced Wire Line
Original Publication Date: 1978-Mar-01
Included in the Prior Art Database: 2005-Feb-20
Fig. 1 shows a communications system 1 for interconnecting a number of data stations 2 with a balanced (twinaxial) line having two conductors 11 and a grounded shield 12. Conductors 11 are terminated at each end with resistors to avoid reflections. Drop lines 13 transmit and receive differential signals for each station 2. Each station contains a driver 21, a receiver 22 and a controller 23. Receiver 22 has a high common mode and differential input impedance to reduce noise pickup and reflections due to line loading. Internal active hysteresis further reduces noise. RC noise filter 24 further increases differential impedance. Diodes 25 isolate driver outputs from line 11 when station 2 is not powered up.