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

[Barton Hodges]

asterisk-users-admin at lists.digium.com wrote:
> The real problem arises when :
> - you have some echo induced somewhere (your call goes through a 2  
> wire line) 
> - you have some delay induced somewhere (you use VoIP for instance)

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

However, the following could result in noticable echo (as I am
experiencing):

- Analog phone <-> ATA <-> Asterisk <-> TDM01B-FXO <-> PSTN
- VOIP Phone <-> Asterisk <-> PSTN

What about the following as described in Raymond McKay's setup (Thank
you Raymond)
Does the channel bank provide the needed, and adequate echo
cancellation?

- Analog phone <-> Adtran TA750 <-> T100P <-> Asterisk <-> TDM01B-FXO
<-> PSTN
- Analog phone <-> Adtran TA750 <-> T100P <-> Asterisk <-> T100P <->
PRI

> In this scenario, echo becomes noticeable, and disturbing. You need
to
> echo cancel at the closest from the source (in the ATA, for
instance).

Since you state that echo cancellation needs to be performed closest
to the source, could the Grandstream HandyTone-286 be doing an
inadequate job of echo cancellation?  If this is the case, does anyone
have experience with another ATA (Sipura SPA-1000, Cisco ATA-186,
etc.) that does such a great job of echo cancellation, that the
"2-wire to 4-wire" situation is not an issue?  Does Grandstream have
improved echo cancellation scheduled for a future firmware upgrade?