CHANGEOVER DEVICE FOR FOUR-WIRE LINE

摘要

PURPOSE:To realize an economical 4-wire line by forming the changeover device with two diodes connecting both ends of a primary winding of a transformer to reception lines, two diodes connecting both ends of a secondary winding to transmission lines and connecting the four diodes in a polarity such a way that all of them are conductive when a DC current is supplied to the lines. CONSTITUTION:The device includes one coupling transformer T0 between a neutral point of a primary winding and a neutral point of a secondary winding of which a relay winding is connected, two diodes D1, D2 connecting both ends of the primary winding to reception lines, and further two diodes D3, D4 connecting both ends of the secondary winding to transmission lines respectively, and the four diodes D1-D4 are connected in a polarity that they are conductive through the supply of a DC current. When a DC switching signal (positive at an input terminal LR) is applied, this signal is fed in a route of input terminal LR diode D1 diode D2 primary winding of coupling transformer T0 relay winding RL diodes D3, D4 output terminal LS, and the relay is excited to open relay contacts rl-1-rl-4.