Originally Posted by
Rataxes
Yes, I couldn't find an image of the set I was referring to but hopefully the image above shows the concept of the guard function for the purpose of the discussion - the original meaning of "guard" versus today's slang and mis-used terminology.
The picture actually confuses the point you're trying to make, because it includes a selector switch with a "GUARD" position.
The guard 'function' to which you referred is the consequence of a separate, dedicated receiver tuned to the distress frequency. For example, the transceiver in the system which includes the controller of which you posted a picture - the AN/ARC164 - there is a separate, dedicated receiver tuned to 243MHz. You will hear transmissions on 243MHz in that system,
irrespective of whether the function switch is set to "MANUAL" or "PRESET" or "GUARD". That separate receiver is 'guarding' the distress frequency, full time. Switching that controller to "GUARD" means the 'main' transceiver will then transmit and receive on 243MHz.