Thanks for your reply.
I'm on the 50V range of the voltmeter and see 40V but on the AC !! Nothing if I check with the DC of the voltmeter. On the 2565, there's a very small ring, that confirms a too low voltage, the one on the Call director don't move at all.

Most of all, I'd like to ear the buzzer. I have the one installed on the Call director, and other one directly purshased new, but none is working. I remember that the one I purshased alone was given for high voltages... If the one on Call director is given for 10V AC, does it mean that I burned it when trying on the line with 40V ?

There's only one phone on the network.