Why does multi-line fax modem not use all lines to broadcast faxes?

[HamzaFassi]

Hi everyone,

I'm using C#, Windows Vista, faxcomexlib dll. my modem is a multi port fax modem (8 lines).

I have two working fax lines connected to my fax modem. when I test each line separately, both are working. When I plug them both and try to send more than one fax at a time, only one line is used, even if both lines are connected and perfectly working.

any help would be greatly appreciated.

thank you!