Network, DSL, Fax

Hey everyone, I have a question about a network. Have a DSL modem going into a 16 port switch, only 6 are being used. There are 3 in the back office and 2 in the front office, there is a network stand alone printer setup in the front office. This printer has a copier, scanner, fax machine and all the works. Everyone can access the internet and print to the network printer, but when a fax is sent or recieved the internet connection is broken until the fax or complete. What could be the cause of this you think??

Note: I thought it could be something to do with a filter but I wasnt sure.

Any suggestions????

 

Yes its a definitaly an issue with the fax machine not being filtured or it giong bad. I do tech support for a company which does dsl support.

 

Thank you, Thats why I was leaning towards being the problem.