307 - beeps when ignition key turned?

I have a 54 plate 307 HDI 136.
Every now and then, when I turn the ignition key to position2 (glow plugs,
etc) the usual dashboard lights come on and then go out as normal, but I
also hear 3 loud-ish beeps (all same pitch). Nothing unusual comes up on
the multi-function display, and car drives fine.
Anyone got any ideas what the beeps are indicating?
TIA

 

That you are about to drive a car?

 

I have exactly the same thing on my 307.

The 307 dealer says I should get my battery tested, but it has been doing it
since I got the car a year ago!

 

ok if you put your keys in the ignition switch it on then off and open the
drivers door (key recognition) is this the same kind of beeps if so its a mux
problem

 

Nope. What I'm getting is 3 beeps the same pitch. The
keys-in-and-doors-open sound is 3 ascending beeps.

 

Does your vehicle have rt3 (sat nav unit) ? ...curious

 

No. Just the bog standard (but quite well-appointed) spec