ok, Im sorry. i try to explain.
This project i am working on is a Hamradio, Amateur Television Transmitter "Radio Frequency Power moduul" that transmit TV signals so people (Hamradio users) can receive it from a large distance.
The equipement are to far away from our hand to control it.
So, to put the device operational it has a switch to turn it on (the relais turn the power on, on the RF moduul). now this part of the equipement is operational. we go home now.
Afther a few day's it seems that the Fan to cool down the RF module, is not working anymore, maybe we have buy a cheap one,,
This Fan is cooling the RF module from the transmitter. When this module is to high temperture it will be destroyed.
1, the on/off switch outside the 19" cabinet must toggle the relais on
2, the fan has it's own control in the code, using for example the LM35
is this clear for u?