[Asterisk-Users] Best echo-free and trouble-free system?

[Rich Adamson]

> > Following the "2-wire to 4-wire causes echo" thought, the following
> > should not result in noticable echo, true?
> 
> > - Analog phone <-> TDM10B-FXS <-> Asterisk <-> TDM01B-FXO <-> PSTN
> > - VOIP Phone <-> Asterisk <-> VOIP Phone
> > - VOIP Phone <-> Asterisk <-> T100P <-> PRI
> 
> All of these have the potential for echo.  Your analog phone is a 2-4 wire 
> hybrid (ear and mike -> 2 wire) -- the FXS and FXO modules have 2-4 wire 
> hybrids...
> 
> I suppose it's more of an issue of quality of the hybrids.  I have been very 
> happy with the TDMxxx hybrids, and very unhappy with the X100/101P hybrids.
> 
> VOIP phones can throw a DSP at the echo problem and will generally have great 
> success since the ear and mike interfaces are pretty much standard -- you 
> don't have unpredictable interfaces like you do on the PSTN side.

FWIW, historically the echo/hybrid issues and dealing with echo are far
more of a problem at the pstn interface due, in part, to changing conditions.
The changing conditions result from temperature changes (impacting certain
forms of pstn plant), wet cable, how well certain items of equipment
within the Central Office are maintained, age of that equipment, etc, etc.

Funny some enterprising member of this list hasn't come up with a marketing
plan to sell commercial line equalizers and/or echo cancellers to x100p
users, TA750 users, etc. ;)