Read Panasonic KX-T7665UA (serv.man3) Service Manual online
9
KX-T7665UA-B
4.2.4.
Reset Circuit
Reset Signal is outputted from IC7 and inputted into IC2,
IC3 and IC6 at the connection of TEL cord.
IC3 and IC6 at the connection of TEL cord.
4.2.5.
Power Supply Circuit
This circuit converts the voltage supplied from PBX into the power supply voltage of +3.3V by IC1 (Switching Regulator IC).
Q22 and Q23 control the power supply circuit as below to turn IC1 on in low consumption current at starting up.
Q22 and Q23 control the power supply circuit as below to turn IC1 on in low consumption current at starting up.
• Input Voltage approx. 26V or less
→Q23 OFF →Q22 ON →IC1-pin 3 H →IC1 OFF
• Input Voltage approx. 26V or more
→Q23 ON →Q22 OFF →IC1 ON
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