Fax Setup says "phone line not connected"

[MFS]

I have had my HP multi-function color LaserJet Pro  printer (MFP479dfw) for some time and I love it.  But, I had never had a need to set up or use the FAX feature until today.  When I tried to use the FAX Setup wizard, it kept telling me that the "phone line is not connected".  After several false starts, I got it working and learned several lessons along the way that I would like to pass on to others who might have the same problem.  To cut to the chase, it turned out that my main problem was that I was plugging the phone line cord into the wrong place on the back of the printer.  When I looked at the back of the printer for a place to plug in the phone line cord, it appeared that there were only three input jacks on the back of this printer.  One USB jack that was obviously a USB port and two other jacks of two different styles, but each labeled with a network symbol.  One of those jacks fit the phone line connector perfectly so I plugged it in to that jack.  WRONG.  After using a phone to confirm that the phone line was indeed good, but still getting the error message in the FAX setup wizard, I started looking more closely and discovered that the two actual phone jacks on this model printer are hidden under a removable plastic cover on the upper right back of the printer as viewed from the back of the printer.  I plugged the phone cord into the left (line in) jack  as viewed from the back and presto, everything worked fine.  Once the cord is plugged in, the plastic cover is designed so that it can be reinstalled with one or both (in & out) phone cords in place.  While I am writing, a few other things I learned that might be helpful if you are having phone line problems.  First, the HP printers are designed to only work with two-conductor phone cords, NOT four conductor phone cords.  The one that was shipped with the printer is a two-conductor phone cord as can be seen by looking closely at the connectors on the ends of the cord that have only two metal strips in the contact area.  Many telephone cords are four-conductor cords that have four metal strips in the contact areas on each end.  These apparently don't work with HP printers.  Second, if you have a Digital Subscriber Line (DSL) phone service as I do (I use DSL for my high-speed internet connection), then you need to install a DSL filter module between the phone line wall jack and the line to the printer.  This enables the printer to send analog FAX signals on the DSL line.  The filter can be a four conductor unit, but just be sure to plug the filter into the wall first, then plug your two-conductor phone cord into the filter unit and then into the printer.   I hope this helps someone else avoid some of the frustration and wasted time that I experienced today.  Happy FAXing!