Ah but the G3's can emit a single service beep if the service timer has been programmed,engineering programming,flag B.
Take gts's advice because he's correct in thinking the beeping was from a smoke/cmox detector with a low battery located nearby :),
I had a call years ago from a customer who still demanded an engineers visit even after I told him the beeping wasn't from the system,and was more likely to be a low battery in a smoke or cmox detector.
"Nope it's from my alarm,so send engineer" so we did,turned out it was a c moxl detector under an untidy pile of mags/old newspapers
near the fireplace :D.
He cancelled his service contract calling us rip off merchants when he was given the bill which I stressed over the phone he'd have to pay if engineer found no faults with his system.
So if an exp engineer says "it's a smoke or c-mox detector",then it usually is .
e manno
August 2013