Hi, Marcos,

So here is my take on this: It's an Edwards (brand) or equivalent buzzer 
mounted on a wood sounding board driven by some sort of motor or relay 
and picked up with a microphone in a fairly live room.

A buzzer (like a bell) were common in my youth (50s and 60s) at hardware 
stores. Wow they are still available:
More info about Edwards:

The basic mechanism is shown here:

At the left, the contact is broken when the electromagnets attract the 
armature, driving the clapper into the bell. When the contacts open, the 
magnetic field collapses and the spring pulls the armature away from the 
coils. When contact is made again, the electromagnets pull the armature 
back. Hence the repeated buzzing or ringing.

The clunking relay or motor driven cam switch was obvious at the 
beginning of each buzz cycle.

So that is the likely source of the sound. What it means, I don't know. 
It is a mechanism that any electronics hobbyist of the day could have 
thrown together.



On 2017-06-13 12:49 PM, Marcos Sueiro Bal wrote:
> This is from a 1968 International Interview recording. It comes after a 1kHz tone and seems like some kind of alarm, but it is reportedly not part of any Emergency Broadcast System nor CONELRAD. It is unknown whether this sound was actually broadcast.
> Thanks for any help!
> Marcos Sueiro Bal
> Senior Archivist, New York Public Radio
> 646 829 4063
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada                             647 479 2800
Quality tape transfers -- even from hard-to-play tapes.