KX-TDA0103X, KX-TDA0103XJ, KX-TDA0104X, KX-TDA0104XJ, ETX1KM753MB, ETX1KM752MB - Panasonic PBX Service Manual (repair manual). Page 14

14

This section provide the shutdown function when any of the following condition occurred; 

i) Over voltage is detected on any of the outputs
ii) 15V output is shorted for a slightly extended period of time
iii) Over heating is detected on the secondary heatsink
iv) Over heating is detected on the Primary heatsink (Signal is supplied directly to primary PWM IC001)

TS001 : Primary Heatsink over heat detecting thermostat
TS101 : Secondary Heatsink over heat detecting thermostat
IC164 : 15V over current detecting IC
R208 : 15V current sensing resistor
ZD201 : 15V over voltage detecting zener diode
ZD301 : 15VP over voltage detecting zener diode
ZD501, ZD502 : 30V over voltage detecting zener diode
ZD103, ZD107 : 41V over voltage detecting zener diode
PC002 : transmit the abnormal detection to the Primary PWM to latch off.