[HELP] - Selective gain adjustments

Hi, I was wondering if anyone knows if the following is possible:

Can the rxgain and txgain be altered in the extensions.conf macros along with a re-read of the configs dependent on the type of call coming in ?

The reason is because of the following issues that I have:

With rxgain and txgain set to 0.0 voice calls from the PSTN via a TDM01B are quite acceptable (and no real echo probems). However fax calls are recognised but do not get processed (after a timeout a hangup command is issued) But, if rxgain is set to 15.0 and txgain to 5.0 faxes are processed perfectly, the downside is that voice calls suffer badly from echo (really bad to start trailing down to just about workable).

I’ve noticed that during a call I am able to change the settings in zapata.conf and then re-read the configs so that the voice call is good again. All this without the call being disconnected.

So therefore I thought that I could set zapata.conf gain levels to that required for voice calls, and then perhaps in exten.conf (ext_fax macro) the gain levels adjusted along with a config re-read to enable faxes to be processed. At the end of the macro the gain levels could then be reverted back and configs re-read just before the system goes back into wait mode.

So does anyone think this is possible, and if so what code would I need to insert ?

My current setup is A@H 2.8, Digium TDM01B for PSTN, Celeron 2.4 with 512 meg ram, GXP-2000 and BT101 phones and I’m in the UK.

Any help would be greatly appreciated, thanks in advance.