Adrian wrote:
PC Paul ) gurgled happily, sounding much like they were
saying


TBF, I'm not sure whether the vibrating "ring" is a motor whirling a
weight about or a solenoid or what.

It is.

It is which?

http://www.huahongnet.com/Vibration.htm

Ah, it's a small "thingy" of varying shape. Helpful.

Sorry... it *is* a small electric motor with an eccentric weight attached.