The only thing you can adjust in the TA as far as the audio, is the attenuation. Under the FXS module there is "Tx (dB)" and "Rx (dB)". These are with respect to the T1 (transmit out the T1 and receive from the T1) and are negative dB values. So "0" is the loudest they can be adjusted, and can go to 10 dB attenuation. Otherwise it is simply a channel bank connecting the FXS port to the channel on the T1.
For disconnecting a call, the FXS module is looking for either a short between Tip and Ring to hang up the port, or an open between Tip and Ring to go off-hook on the port. You can look at the STATUS of the module to see what is being transmitted. (For Loop Start signaling, TA=0 and TB=1 is idle/onhook and TA=1 and TB=1 is offhook. If it is Tandem E&M then TA=0 and TB=0 is onhook, and TA=1 and TB=1 is offhook.)
If you have 2 TA850 channel banks, you can connect them back to back with a T1 crossover cable, and then configure the FXS ports as Tandem E&M and it will act as a PLAR connection, so when you go offhook on one side it will ring the mapped port on the other side - and then you can verify audio, etc.
Not sure if this helps or not.