GRAUPNER mc-16 Programming Manual page 272

Basic settings
BT Headset
BTH002
ID PAIR OK
BT Volume
... you can adjust the volume of your BT device us-
ing the same procedure described earlier for adjusting
volume for the "Speech volume", "Vario volume" and
"Button volume" options.
272 Program description - Basic settings
A2DP
1/3
ON
8
SEL