Faxing from a Mac over ISDN

My ISDN phone has two cables going to it. One looks like a standard RJ11, the other is similar except that the little hook-thingee is off to the side instead of centered, as with the RJ11. I assume this is the digital line. When I stick the RJ11 plug into my iMac modem port and attempt to fax, I hear no dial tone and the fax status icon on the menu bar shows that the modem keeps trying unsuccessfully to dial. I was under the impression that one could fax from an internal modem over an ISDN line. Not so? If so, is there some sort of setting I need to configure?

Nope, analogue and digital modems are totally different. In fact you normally fry an analogue modem by plugging it into a digital line, so unplug it. Your telecom provider may have supplied a converter, if not you need one, or get a digital modem instead.

Thanks for the info. Since you seem knowledgeable about these things, may I ask you something else? Why are there two cables going to my ISDN phone? And what are their respective purposes?

Don't know, sorry.

Tell us the make and model number of your phone, and maybe more help with be forthcoming. All phones are different and have different capabilities