'unexpected error' prevents fax being sent

[Sebastian42]

USB fax unit connected to a Win8.1 desktop. All seems to go well [in contrast to previous attempts where step by step I overcame numerous obstacles). The fax was the ONLY [and first] connection to the landline. The 'unexpected error' message comes after 'sending first page'.

 

[LoPath]

Unfortunately there are a lot of other things that can cause a fax to fail. A couple of examples:
1. Your landline is shared with DSL (must have a filter, but still may not work with one)
2. Your landline is shared with a T1 (which can happen without your knowledge)

Do you have a regular fax machine that you can test the phone line with?

LoPath

 

[Sebastian42]

I have a fax machine that used to work. It was when that became dysfunctional that I decided to try the USB/FAX option of my PC. First in Win7 where I could get no traction. But then in Win10, all the PRELIMINARY problems disappeared. Eventually in Win8.1 which is the closest to the point where the phone line enters the Unit.