asterisk users - Feb 2016 - 11.21.0 : echo woes : can't installcanceller (sean darcy)

Hi Sean

In case of electrical I think DAHDI card if could have the capability by a
combinations of jumpers it will be too hard to set best level, think about it 
for one or a wide device,  could take long time for start-up, and will require
to adjust or controller periodically,  therefore many terminal devices could
have it inside, by changing jumpers or some components to adapt according to
electrical line condition
By the other way  market analogue terminals  mainly follows,  to FCC or European
standards, I remember these kind of symptom  happens with Panasonic KX-TS500,
whatever PBX or line it feels echo.
In case of acoustic  analogue device it used analogue circuit, SIP used DSP
(Digital signal processing circuit) these last one is better than analogue
system.

Mc GRATH Ricardo