TelCos, fast-busy signals & 10-10 services. Headaches of the mysterious phone world.

Okay, Dopers, the world of telephone companies confuses me, despite the fact that I have been managing parts of it for years.

Here is the dilemma: One of my groups has about 50 customers who fax numerous things daily. Ah, nothing like piles of paper and all the fun associated with that. So, we get with the program and set up a fax server. All seems fine. We even have the docs go straight into our electronic doc workflow, and don’t need to scan faxes into it anymore.

Then a problem pops up: About 15 companies who have always sent faxes to our old fax machine(s) haven’t been able to get one fax to us since we cutover to a fax server.

They always get a fast busy signal. They are the only ones who get a fast busy.

Someone suggested they dial 10-10-220 before a fax attempt, and lo and behold, the calls always complete when they go that route.

What in bejeezus are they accomplishing when they dial 10-10-220 that enables them to connect, instead of hearing a fast busy?! Don’t the calls ride the same copper and/or fiber all the way, regardless of who the carrier is?! :confused: