KX-NSX1000, KX-NSX2000 - Panasonic PBX Service Manual (repair manual). Page 15

15

Part 6 provides a description of the overvoltage/overheat protection circuits
(1) Abnormal State Detection Circuit. 

If power operation becomes abnormal and a signal is transmitted to the abnormality detection circuit  D112, Q112 is turned on,
current flows to the diode of PC2 and is transmitted to the control circuit of the main converter, thereby shutting down main con-
verter operation. 

(2) Overheat Protective Circuit

When temperature inside the power source rises to an abnormal temperature, the resistance of posister PTC101 rises, transis-
tor Q112 is turned on, and the signalis transmitted to the abnormality detection circuit via D125.

(3) Overvoltage Protective Circuit

If the 15V output is high (overvoltage), D112 detects it and transmit to the abnormal detection circuit via D113.