[asterisk-users] ISDN30 and TDM400P + FAXing ...

[Andrew Joakimsen]

Assuming your PRI supports timing from the remote end (CO) which I
highly suspect is the case, then you should set the asterisk machine
to be a slave to the CO timing and then set any other interfaces  you
have to NOT be masters, so that the CO timing is always used. Assuming
you do this and disable echo cancelation then there should be no issue
if the entire path is low latency (IE not over the internet, not over
a VPN gateway and not over a WAN unless you have end-to-end QoS and
even then you could have latency issues, of course T.38 would solve
almost 100% of any issues that these would induce in your system, but
Asterisk does not and I higly doubt it will support anything besides
T.38 pass-through which wouldn't work with any sort of PSTN interface
you could use with Asterisk)

On 1/20/07, Gordon Henderson <gordon+asterisk at drogon.net> wrote:
>
> I have a system I'll be installing soon which has an ISDN30 (E1, UK) feed
> and they want to hook up a fax machine and use existing analogue
> conference phones (expensive polycom units)
>
> This is something I've seen and used on legacy PBXs and would seem to be a
> fairly standard offering, but an earlier post seemd to suggest that the
> cards would need some sort of timing synchronisation between them to make
> faxing work - can anyone confirm or deny this?
>
> Would there be any issues in the dialplan when seeing a call on the PRI
> DDI associated with the fax line simply Dials the corresponding Zap line
> that the FAX machine is connected to?
>
> Gordon
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