asterisk users - Jan 2006 - E1 -> T1 native bridging for fax, will it work?

Hi list!

The stability of * with fax (or the lack of it) is causing me headaches.

To solve it, I was thinking to put a TE205P card in the * box, connect the 
E1 pri on one port and a channelbank (I was thinking of the Rhino) on the 
other port in T1 mode. (Has anyone tried this??)

The TE205P supports channel bridging which sounded like the ideal 
(but not cheap) solution when combined with a channel bank.

When checking with Digium support if E1<->T1 bridging will work they 
replied:
It is unlikely to work consistently with that configuration, because E1s
typically use alaw encoding and T1s typically use ulaw encoding, and the
ulaw->alaw conversion would be done in software, thereby making a native
bridge not possible.

This makes sense but raises several questions:
- even if * will do the software conversion will the quality of the 
channel remain sufficient to provide rock solid faxing. Maybe the channel 
bank is considerably better than the sipura's I have been using so far and 
there would be no ethernet involved.

- are there any T1 channel banks that support alaw or would I be forced to 
either buy an E1 channel bank or use a legacy PBX as channel bank

- who decides which encoding is used, zaptel or the channelbank (in other 
words, if a T1 channel bank would support alaw, can I force alaw 
only to guarantee native bridging?

Any help / input / thoughts / experiences greatly appreciated!!

Thanks, Remco

Remco Barende wrote:
> - even if * will do the software conversion will the quality of the 
> channel remain sufficient to provide rock solid faxing. Maybe the 
> channel bank is considerably better than the sipura's I have been using
> so far and there would be no ethernet involved.
There will be far less latency and no jitter to speak of doing the 
ulaw/alaw conversion, unlike going over the LAN.
> - are there any T1 channel banks that support alaw or would I be forced 
> to either buy an E1 channel bank or use a legacy PBX as channel bank
I doubt you will find a T1 channel bank that supports alaw companding.
> - who decides which encoding is used, zaptel or the channelbank (in 
> other words, if a T1 channel bank would support alaw, can I force alaw 
> only to guarantee native bridging?
The other device decides; Asterisk/Zaptel can be configured for either 
companding method on any channel.