D2.8
T858/859 Circuit Operation
M850-00
31/09/98 Copyright TEL
If the temperature drops below -10°C, Q21 is turned off, preventing either Q19 or Q20
from activating the fan.
Fan operation may be summarised as follows:
T < -10°C - fan unconditionally turned off
-10°C < T < +70°C - fan turned on only when transmitter keyed
T > +70°C - fan unconditionally turned on.