Why PN/Gateways need a T1 sync?

[HossBoss]

Does anyone have a good explanation on why a PN and/or media gateways need a T1 sync source? I've read that you can have faxing issues when using FoIP (which we are doing...and having issues) but i'm looking for more supporting documentation or general details.
Any thoughts?

 

[rejackson]

Are you saying that you do not have a T1 or PRI but someone is saying you still need a sync source defined?

 

[HossBoss]

correct...converted 100% to all SIP trunks so no T1 available even as an option. I know SIP and faxing don't play well together as it is so i'm looking for anything that might help either explain part of the problem, or support adding a T1 for the clocking.

 

[rejackson]

When we converted to SIP our fax problems were resolved by setting the codec to use t.38 for FAX, AND set Modem to off. In our case that created problems for our postage machines that were using the modem settings. We had to set up a non-SIP trunk for them to use with another codec that had modem as passthrough.