Ricoh C211 Service Manual page 431

8.
Thermal Head Pulse Generator
Voltage to the thermal head is applied in 24V pulses. The energy applied to the thermal
head is changed by changing the pulse width according to the thermal head temperature
and its resistance.
High
1)
2)
3)
Narrow
1=
1
84 1
High
Thermal Head Temp.
Low
7
I
Average Resistance
o
Low
Thermal Head Resistance
The resistance of the thermal head varies from one head to the another.
The information of the thermal head resistance is sent to the pulse generator.
Head Temperature
The thermal head contains a thermistor, which detects the thermal head temperature.
The pulse generator controls the pulse width based on the above thermal head
resistance information and the head temperature information.
2-19