Brother MFC-9420CN Service Manual page 70

<Controlled Temperature and Safety>
Temperature
( )
C
TS: To maintain the set point (temperature) for fusing of toner to be approx.
160°C as appropriate by turning on/off the thyristor.
TA: Reference temperature (approx. 185°C) to identify that it is excessively hot
inside the fusing unit. When it reaches to this point, the relay RY turns off,
the power supply to the heat lamp is shut down, and the machine stops the
operation.
TPS: Limit temperature to have the thermal cut-off start melting and shutting
down the power supply to the heat lamp if the temperature control circuit
should break down.
Time
Fig. 3-36
3 - 3 6
TPS
TA
(160) C TS
Confidential