Leads Direct sells a wide range of Telecoms cables ready made, including RJ11, RJ12, ADSL cables, and BT 4 and 6 wire cables and extensions. We can also make custom telecoms cables to your specification on request. You can view and purchase them by visiting our secure online shop which has literally thousands of products each with two sizes of image.

However, there may well be times when you need help to find wiring information, to make your own leads or to repair an existing installation, and that is the purpose of this page.

Connectors

Two different types of modular connector

The connectors used for Telecoms wiring are usually referred to as 'modular connectors. There are a number of different ones available, the most common being shown below:

• 8P8C = 8 Position 8 Conductor (RJ45) - used in Network Wiring
• 6P6C = 6 Position 6 Conductor (RJ12) - used in System phones
• 6P4C = 6 Position 4 Conductor (RJ11) - used for ADSL, telephone, and modem cables etc.
• 4P4C = 4 Position 4 Conductor (RJ10 / RJ22) - used for Telephone Handset cables

A pair of BT plugs

In the UK the most common way of connecting a telecommunications device to the telephone line is a BT plug. This is pretty much unique to the UK and comes in two types:

• 431A BT 4 way plug (6P4C)
• 631A BT 6 way plug (6P6C)

The 4 way plug is the standard one used on home and small business telephones. The 6 way plug is commonly used on telephone systems and the extra pins are used to transmit control signals which vary from manufacturer to manufacturer.

 All of these connectors are fitted using a crimp tool, or more commonly several crimp tools since it is rare if not impossible to find a tool that will fit all of them. You will find a huge range of these and other cable related tools in our secure online shop, and a smaller selection on our tools information page.

Cable

All the connectors listed above are usually fitted to flat profile telecoms cable with 4, 6, or 8 cores. The most common colour is white, but black and grey are fairly freely available as is cream in certain ready made lengths. Other colours are available but there may be a long lead time and a high minimum order quantity.

Wiring

A great deal of confusion arises over the wiring of telecoms cables. Many people simply do not realise that the cores of the cables can be arranged in more than one order, and therefore experience problems when they try to connect a cable that originally came from a telephone to a modem, for example.

Confusion also abounds where the term 'direct wired' is used... some manufacturers of telecoms cables usually use this nomenclature to describe the situation where the cable is wired so that if you pull the cable out to its full length without any kinks or twists the plugs would be facing in the same direction, which in terms of pin connections would be a 100% reversal e.g. 1-6, 2-5, 3-4 etc. Others (notably APC) use it to describe a 'straight through' connection e.g. 1-1, 2-2, 3-3 etc.

The majority of manufacturers and distributors use the terms 'direct wired' to mean a full reversal and 'straight through' to mean a straight pin to pin assignment, but it is not safe to rely on this and you are advised to actively check the pin configuration before placing an order or starting to make or repair your own cables.

The most common wirings are as follows:

• ADSL Modem / Router: Middle two on an RJ11 to the middle two on a second RJ11 - it does not normally matter if these are pin to pin or crossed. Normally a four core cable is used, and normally it does not matter if or how the outer two cores are connected.
• ISDN: RJ45 to RJ45on 8 core cable wired straight through.
• Dialup Modem: Middle two on an RJ11 to the outer two on a BT 431A using two or four core cable depending on the make. Some will not work with a four core cable connected.
• BT Domestic Telephone: RJ11 to BT wired straight through on four core cable.
• System Phone: RJ12 to BT631A wired either straight through or a complete reversal depending on the manufacturer, always on 6 core cable.

This listing is by no means exhaustive, and one of the most common problems reported to Leads Direct is not being able to get a cable configured correctly for the equipment. Luckily, Leads Direct offer a service whereby you can send in your original cable and have it tested and the wiring identified free of charge. If it is a standard format the correct cable can be supplied. If not, a custom lead can be made to almost any length required.