When you push the CVR TEST button you will get a continuous tone through the loadspeakers for a few seconds before it stops, you keep the CVR TEST button pressed and then it will start with a short beep every 4 seconds or so:
beeeeeeeeppppppppppppp --- 4seconds --- BEEP --- 4seconds ---- BEEP
and so it goes on. Even with the loadspeaker OFF you should still hear your own voice in between beeps when you transmit on the intercom through your handheld mic.
Sounds bloody complicated, but it ain't.