Telephone Wiring Diagram - Ask-The-Electrician Wiring a Telephone Jack After installing the Cat 3 - 3 pair phone wire I am ready to install the wall jack. You will have a wide variety of telephone jacks to choose from but the wiring for a single line phone service will be standard. Doing your own telephone wiring Doing your own telephone wiring. Note: this page describes the phone wiring conventions in the United States. I'm not familiar with the phone wiring conventions outside the U.S., so the information here may not apply in your country. X16 Small Business Phone 110 Wiring Diagram The X16 small business phone system can be wired in various ways. In this guide I'll show you one example of how to wire the X16 system with 4 pair twisted pair cabling in a 110 wiring block. Wiring Information - Telephones UK The wiring diagram for a master LJU socket is shown here. Note that the pictorial view shown above only serves to indicate the two differing types of sockets and wiring connections. Contrary to how it might seem, C1 is connected to terminals 2 & 3, not 1 & 4.