What's this?

[Wingedharpy]

DS moved into house recently.
This object is on a wall, at ceiling height, in a bedroom.
When lights are turned on in room, it makes a low, clicking noise.
Noise stops when lights are off.
Previous house owner deceased and no-one else knows what it is.
Any ideas folks?

If you Google it - it says it is a sound bomb!! My guess is it is something to do with a burglar alarm.

We've got very similar and, yes, it's the bell for the burglar alarm.

Many thanks @Wigglypasta .
I had tried Google but came up with all sorts which wasn't applicable.
DS will sleep more soundly now they can be reassured it's not a Russian spying device!😉