Altigen AltiWare ACM 5.1 Administration Manual page 185

Parameter
Transmit to CO
(dB Gain)
Description
Slide setting adjusts the gain from the trunk to the CO from
0 dB to -7 dB for every Quantum Trunk channel.
The default setting is 0 dB
to change this setting.
Caution! Setting the volume too high will cause distortion in
voice quality and/or missed DTMF digits.
AltiWare ACM 5.1 Administration Manual 171
Chapter 12: Trunk Configuration
, and it is highly recommended not