Brother HL-2600CN Service Manual page 89

TS: To maintain the temperature for fixing of the toner at approx.
146 C by turning the thyristor on and off.
TA: Reference temperature (approx. 185 C) to identify that it is
excessively hot inside the fusing unit. When it reaches this
point (approx. 185 C), the relay RY turns off, the power supply
to the heat lamp is shut down and the printer stops operating.
TPS: Limit temperature when the thermal fuse will start to melt and
shut down the power supply to the heat lamp if the temperature
control circuit should break down. When the thermal fuse
melts, the printer will stop operating.
<Safety Control by Temperature Control Signal>
H0: When the THERR signal is input, the control panel indicates
"H0", and the printer will stop operating.
H2: If the temperature of the fixing unit does not reach the required
point "T1" after a certain time, the control panel indicates "H2"
and the printer will stop operating.
H3: If the "Heater On" signal still continues after a certain time, the
control panel indicates "H3", and the printer will stop operating.
H4: If the temperature within the fusing unit becomes unusually hot
and when ACOFF signal is input, the control panel indicates
"H4", and the printer will stop operating.
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