IFF mis-use in WWII was a fairly well described in a book "The Wizard War" by Reginald Jones. The allies were losing an unconcionable number of bombers to German radar and RF detection systems. These were all new to both sides and consistantly misused until the problems were obvious. The British bomber crews seemed to have the impression that the IFF units would somehow affect the anti-aircraft batteries and their search lights. So, against orders, they would turn on the IFF transponders, giving the Germans substantial warning as to the time and direction of a bomber attack. They never could resist turning it on so they were eventually removed and not used.
No. The BC-645 was really crude. Worked at 420MHz using a "doorknob" tube. The receiver would decode two pulses with controlled spacing. If the spacing was right, it would respond with an AM modulated tone burst. The later AN/APX-6 worked on about 800-1200Mhz and worked somewhat like the current civilian radar transponders (encoding altimeter). The British had similar systems with different designations:
I'm not too worried. If the military actually turned everything on all at once, nothing would work, everything would interfere with everything else, and the whole mess would probably blow a fuse. I've seen it happen. Sorry, no details.
A code plug and a key. It required 24VDC from the aircraft to initiate the charge.
Neither. The military was deploying the SCR-584 radar at the time for anti-aircraft gun control. It has the bad habit of shooting down anything that flew overhead. The idea behind IFF was to prevent friendly fire from shooting down the bombers as well as warning night fighters that they have an enemy target.
I obviously didn't try it to find out if there was a delay. I suspect it was instantaneous initiation.
Learn by Destroying(tm)?