Thanks to all, many good ideas there !

My issue is not with the phone ringing, as no phone is allowed in my darkroom (the phone is a "business" one and I keep the damn thing shut of as much as is realistic), but the backlight.

My current timer is an LCD one, so it is unreadable in the dark.

I like the idea of using music, this looks an exciting idea, and would save me from a boring record of my own voice.

Chees !!!