Night telephone service light circuit (1)

Circuit working principle: R1, VD1, VD2, ZD1, C1. A simple rectifier and voltage stabilizing
circuit is formed to provide the working power of the circuit . L1 and L2 receive telephone lines .
When the phone is dialed , the ringing signal generated on the line is coupled through C6, rectified by VD4 and VDs , and filtered by C5
, so that the photoelectric receiving tube of the optocoupler is turned on.