AOpen FM56 Manual page 117

This command causes the modem to set the microphone gain of the speakerphone
function.
Syntax
+VGM=<gain>
Defined Values
<gain> Decimal number between 0 and 255 corresponding to the gain.
Reporting Current or Selected Values
Command: +VGM?
Response: +VGM: <gain>
Example: +VGM: 0 For the default setting.
Reporting Supported Range of Parameter Values
Command: +VGM=?
Response: +VGM: <gain> range
Example: +VGM: 0-255
Result Codes
OK <gain> = 0-255.
ERROR Otherwise.
5.2.3.4 +VGS - Speaker Gain
This command causes the modem to set the speaker gain of the speakerphone function.
Syntax
+VGS=<gain>
Defined Values
<gain> Decimal number between 0 and 255 corresponding to the gain.
Reporting Current or Selected Values
Command: +VGS?
Response: +VGS: <gain>
Example: +VGS: 0 For the default setting.
Reporting Supported Range of Parameter Values
Command: +VGS=?
Response: +VGS: <gain> range
Example: +VGS: 0-255
Result Codes
OK <gain> = 0-255.
ERROR Otherwise.