[cbpowell]

Wikipedia has a very nice writeup on the device: https://en.wikipedia.org/wiki/The_Thing_(listening_device)

They stress it had no active electronics. The imagery in the article clearly shows it had some metallic innards, presumably these are passive electronics for modulating the illuminating signal.

[kevin_thibedeau]

It's just an antenna and resonant cavity. No wires involved. The modulation was performed by the mechanical vibration of the diaphragm.