And while I'm here, what is the JPT Control? Is it to allow Military Power to be used without over-temp warnings? Probably not.
forget,
Although I cannot give you exact details of the Victor JPT limiting system due to the fact I'm not a Victor man, most aircraft of the time had a similar kind of JPT control system.
The JPT Control system is in place to ensure that the engine does not exceed a maximum set JPT limit at Max Power, in order to maximise the engine life. This can generally be over-ridden by the type of switch you see, so that the engine will then be controlled by the Maximum RPM governor loop, and the engine will be allowed to 'overtemp' and run faster for a short time in order to produce a maximum amount of power, such as a Max AUW take off for example.
Hope this message finds you well
Flipflopman