CONELRAD — I have a 1959 ARRL handbook that has a Conelrad circuit design. In case of suspected nuclear attack (by bomber, not guided missile), radio stations were supposed to shut down, they thought the planes might use radio direction finding to navigate. The local radio stations would get a call telling them to shut off, and this circuit would detect a local station shut off and cut out your ham radio transmitter. You were supposed to tune to 640 or 1240 AM to hear any civil defense messages.. apparently they’d rotate what stations were transmitting it to make it harder to direction find them. (Although, rotating wouldn’t work very well here, where all the local stations towers are like 50 feet apart 8-).