In stereo.

Hmm, good question...in any case, there is a signal on both channels, but I can't say whether it's stereo or mono on two channels, I've never listened that closely😀.
All in all, I'm very happy with it, and it still works even if the transmitter and receiver are not in the same room.
The only thing is that the display is very small and can only be operated with reading glasses from 50i upwards😂.