Re “It requires a listening/recording/transmission device in or on the outside of the room”.
Maybe I’ve been watching too many crime, war, and SciFi shows but I’ve heard that you can actually use an existing electrical wiring system to eavesdrop by internally turning on a radio, phone, etc. That becomes the listening device and picks up sounds in the room which are then transmitted back along the electrical wiring to a machine that can record them.
Anybody ever heard of this technique or am I watching too many Mystery Theater 3000 shows?
“...you can actually use an existing electrical wiring system to eavesdrop by internally turning on a radio, phone, etc. That becomes the listening device and picks up sounds in the room which are then transmitted back along the electrical wiring to a machine that can record them.”
You would be correct. EMI filtering of the power supply is required and EMI screens on all openings in a shielded secure facility. I wouldn’t say squat in the Oval office. The Oval office windows are a big concern to me. There are much more powerful directional microphones today.
You can never watch “too many” mystery theater 3000 shows.
I recall something like that being talked about back in the 60s with respect to the transducer in a cradled phone. It, like any other transducer in the room (speaker etc) would vibrate and produce micro voltages that could be picked up.