| 摘要 |
1475383 Data transmission; signalling by D.C. HASLER AG 11 July 1974 [12 July 1973] 30796/74 Heading H4P A receiver arrangement for switching out a low/high level converter when high level signals are received comprises a relay normally unenergized, with the inputs to relay circuit and converter in parallel, and energized by high level signals which reconnects relay input circuit and receiver input to line in series, output of the converter being disconnected. An asymmetric device with inverse resistance/voltage characteristic may modify resistance of the relay input circuit. Current from lines 1, 2 pass through protective diodes 3 also one of light emitting diodes 5, 8 which at low level is insufficient to turn on one of transistors 6, 7 a fence energize relay 10; through a contact 11 low/high level converter 14 is energized, the output being connected to a receiver 15 through contact 13. High level input causes conduction of phototransistors 6 and/or 7 which through amplifier 9 energizes relay 10 hence reversing contacts 11- 13 thus disconnecting converter 14 and connecting receiver 15 in series with lines 1, 2. Amplifier 9 has a delayed drop out of a few seconds to bridge current interruptions. On single current working; with double current, this is not so important as one of reverse parallel diodes 5, 8 is normally conductive.
|
