How to Set Up a Fax When You Have a Single Line Telephone Connection

By David Pepper

Updated February 10, 2017

i Zedcor Wholly Owned/ Images

Faxes are a convenience, but they also can be complicated to set up. The usual solution to having both phone and fax services is to have two phone lines, one for the phone and one for the fax. That way, the fax is always available, and voice calls don't interfere with receiving faxes. However, it can cost hundreds of dollars a year to have a second phone line, so if you're not a heavy fax user, you may want to share your single voice line.

First method: At the back of your phone (not at the wall), unplug the jack from the phone and plug it into the "Line" jack on the back of the fax machine. Now take a separate telephone line and plug one end into the fax phone jack labeled "Ext" (for extention) and the other end to the phone.

Second method: Purchase a phone adapter splitter jack (it lets you plug two lines into a single line jack) and plug it into the phone wall outlet. Connect one side of the splitter jack to the back of your phone, and connect the other side of the splitter jack to the "Line" jack of your fax.

With either method, consult your fax manual and set the fax to the "tel/fax" setting. The fax should pick up and connect if you have an incoming fax call, or allow you to answer if you have an incoming voice call. If your fax has trouble determining whether an incoming call is a fax call, you will need a fax switch.

A fax switch will intercept incoming phone calls and route them to your fax or phone as appropriate. There are many brands. The Fax LineShare website explains how fax switches work and shows a typical connection diagram. Connect your fax switch to your telephone line, then plug your fax and telephone into the labeled ports on your fax switch.

Items you will need

  • Fax machine

  • Extra telephone line with plug in jacks

  • Phone adapter splitter jack

  • Fax switch


With a single-line telephone connection, you can't talk on the phone and receive a fax at the same time. If that's your goal, you'll need a second line.