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incoming fax half complete over isdn

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tfm

Technical User
Apr 3, 2006
2
GB
Nexpan pbx connected to two TO basic rate circuits with gsm routed connected to SO port of pbx. Both pbx and gsm router are connected back to main NT for clocking.

What happens is when the fax receives an incoming fax, only half of the page will be present.
 
So basically it hangs up half way through the first page every time?

Does this occur on both outbound and inbound faxes?

Out of curiosity, if you use fine mode does it stop at less than half a page?

My guess is that is probably hanging up after some fixed period of time - try to determine how long this period is. If you use the handeset on the fax machines and place a call and talk do the line hang up after this same period of time is the call terminated? If not do you get a bust of noise or lose audio in one direction or anything else odd?
 
Only on inbound faxes.

If the gsm router is powered down the faxes are fine, so my gut feeling is that it is more of a clocking issue or some programming on the pbx that might sort this?
 
I agree, it sure sounds like a clocking issue.

I would confirm that the GSM is really using the CO clock not an internally generated clock.

I would also try claling into the system and listen for a peridoci (as in every so often) click. If you can hear it then tim eit. If it happens at a regular interval then you defintley have two clocks that are not synchronised.

As I reality check you might try a different fax machine. I saw a situation once with a modem that for some reason would lose it on certian PBXes. As the manufacturers we couldn't really tell what was goign on other than the fact that the modem processor load was peaking out periodically for no reason, only on these PBXes (in other words it was not a simple case of bad noise or frequency response impairments).

If another fax machine works it MAY be possible that the current fax machine has some hidden menu options that cusotmer support could have you change. Of course investigate the clocking issue first.

Good luck.
 
Clocking issue! I know that on the Mitel phone systems, the analog ports go to pot when the sync source is bad. I think that the equipment sometimes needs a good sync source as well, not just the basic/primary rate line.


**************************************
My Biggest problem is that I almost always believe what I tell myself.
 
I've had this happen with a PRI circuit and a Norstar. Voice calls were fine in or out but if you tried to fax in anything over 1 page it would disconnect. It did turn out to be a clocking issue.
 
Just to add it also would drop anything connected to a modem after about 30 seconds. So to sum up any voice calls had no problems but if I attempted any data over the PRI it would drop.
 
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