Panasonic KX-FP85 Service Manual page 139

6.3.9. SUPERVISION CIRCUIT FOR THE THERMAL HEAD TEMPERATURE
1. Function
The thermistor changes the resistor according to the temperature and uses the thermistor´s characteristics. The output of pin
169 of IC501 becomes a low level. Then when it becomes a high level, it triggers point A. In point C, according to the voltage
output time, the thermal head´s temperature is detected.
After the thermal head temperature is converted to voltage in B, it is then changed to digital data in the A/D converter inside IC501.
The CPU decides the strobe width of the thermal head according to this value. Therefore, this circuit can keep the thermal head
at an even temperature in order to stabilize the printing density and prevent the head from being overheated.
CROSS REFERENCE:
6.4.3 THERMAL HEAD(P.142)
139
KX-FP85