Terminate and label the station cables on the right side of a 66 M150 split block or blocks depending on number of stations. Make cords with one modular connector and terminate them on the left side of the 66 block and label them with the extension numbers. Plug the cords into the appropriate extension jacks on the control unit and place bridging clips on the 66 block to connect the equipment to the station wiring. You can also use a patch panel and label one set of jacks as station cables and another set as extensions with patch cords between. The customer can then do his own station rearangement. You can use the aux. jack on a 18d for a fax but you can't be on the fax and the phone at the same time. I usually just assign another extension number to the fax if I have a spare.