Dynamically gain control for analog port?

We have used Asterisk to be our own conference server using Meetme. We use TDM400P to interface our PBX via analog port. However, the volumn of analog voice port is varied a lot by our PBX’s FXO or FXS.
I know there is a static gain control in zaptel.conf. But static gain control is no useful in this case because calls can be placed from PBX’s FXO or FXP, which gain is different and we can not help anything on legacy PBX.
Any hinet for dynamic gain control?


Asteris 1.6 has the following new features:
zap set hwgain Set hardware gain on a channel
zap set swgain Set software gain on a channel

However, anyone know if I can apply this CLI command to an existing zap channel?