[Asterisk-Users] Digium TDM400P vs Sangoma A200 for 2 x FXO

[Chris Bagnall]

I've no experience with the A200, so I can't really pass judgement on it. We
have 2 sites with TDM400P cards currently deployed (one with 3 FXO, the
other with 1 FXO and 3 FXS). The site in Northampton with 3 FXO has been an
absolute nightmare over the last 9 months the system's been in place.
Initially we had big problems with echo that no amount of tweaking of the
echo parameters would fix.

Once asterisk 1.2 was deployed, things improved remarkably. I took the time
on-site to properly configure the txgain and rxgain using a milliwatt tone
coming from one of our other servers in a datacentre (rather than relying on
using ztmonitor -v whilst the client was making/receiving calls - you can't
guarantee whether the party they're talking to has *their* gains properly
configured, which means you end up with completely different results on
every call). Once I'd got the gains properly configured, fairly standard
echo cancellation settings of "on" and "echotraining=800" seem to work
relatively well.

One thing worth checking with BT - if you can find someone who can give you
an accurate answer - is whether the Featureline will give you disconnect
supervision. If it will, so much the better, as * 1.2 seems to have usable
support for it. If it works reliably, you can increase the number of busy
tones to detect before a channel is killed (this will massively reduce
incidences of false hangups).

It's still not as good as the building next door where they have 2 ISDN
BRIs, but it works, and I've not had any complaints for the last month since
their box was upgraded to 1.2.

Hope that helps.

(shameless plug - I have a spare TDM400 card here if you're looking to
acquire one at a reduced price - discuss off-list if interested)

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
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