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New Member

Fax pass through and fax relay

Just want to clear a concept here.I read some documents about the fax passthrough and fax relay. It seems fax passthrough and relay is the two ways that fax send over the IP network in a IPT enviroment.

My question is: if the fax is connected via an FXS port off a GW which connects to PSTN via PRI. In this scenario, do both fax mechnism apply?


New Member

Re: Fax pass through and fax relay

This should be no concern to you, as you are "hairpinning" the FXS port to the PSTN PRI interface on the same Router. Fax pass-thru and relay only comes into play if you are transporting the fax in VOIP packets across the network.


New Member

Re: Fax pass through and fax relay

Thanks. That's great. Btw, I happened to hear the term hairpin couple times, but still not very clearly understands it. Can u tell me where this hairpin concept originally come from? what exactly does it mean? Just for my curiosity, thanks