DTMF regeneration


I would like to disable DTMF regeneration from Asterisk once a
communication is established. Is there any way to achieve that?

For instance when a call is established between to analog phones
and I press continuously a DTMF key for 10 s the remote phone hears the
begin of the DTMF signal and later on a clear DTMF signal of ~125ms.
It seems that the last was regenerated by Asterisk.
What I want to have on the remote phone is a clear DTMF tone of 10s

Thanking you in advance,