There are old household alarm systems based on this tech from the 70’s. I think there were two components - VHF transmitters, and a receiver – and if the receiver detected an change in the receiving pattern, it was because something moved between a transmitter and the receiver, and it would trigger.
There are old household alarm systems based on this tech from the 70’s. I think there were two components - VHF transmitters, and a receiver – and if the receiver detected an change in the receiving pattern, it was because something moved between a transmitter and the receiver, and it would trigger.
Fuck I’m old.