Oh, yes. There were a couple of ready-made CONELRAD receivers available to broadcasters, which would fit in a standard 19 inch rack. They were built to decode the 15 seconds of 1 KHz tone coming in from the regional master station, close a relay that would unmute the audio to the built-in speaker, and actuate whatever else you wanted, like a flashing light or a buzzer.
The cheapie receiver that most small stations used was a “Miratel;” basically a standard 5-tube chassis mounted on a rack panel with the tone detector and relay circuit added on. It went for about a hundred bux back in 1960. Of course almost the same radio in consumer table radio form would have been about 10 dollars at the time.
You monitored a station upstream in the hierarchy (usually a large regional or clear channel) who had direct connection to “HQ.”
When the alarm went off (and if it was NOT A TEST) you’d tune to, as you said, either 640 or 1240, where a regional CONELRAD station would go on the air (where it might already be on the air full time as a regular broadcaster). It would have the teletype connection to get the actual emergency message read out on the air, and to stay on the air during the emergency.
If you were a downstream station, your only obligation at that point was to notify your listeners to tune to the CONELRAD frequency, and then get off the air yourself.
You did, however, conduct weekly tests at various times when you could spare a cheap minute of air time. Every station had either a 1 KC (the Hertz wasn’t invented yet!) oscillator, or a 1 KC tone on tape or disc. Best of all was when you had the whole test announcement on tape. Then you could go for a (quick) break, because the whole test was canned.
Ah, the ravages that time doth wreak upon mine memory!
You had to be there at the beginning of the test anyhow, because you also had to dump the transmitter and bring it back a couple of times before the tone, so that cut down on your possible break time