Lighting circuits

Switches

A simple electric lighting circuit consists of one light and one switch. However, lighting circuits can be wired in a number of configurations with multiple lights and switches. To enable these configurations, manufacturers produce a variety of switch types. Common switch types used in lighting circuits include:

• one way (single pole)
• two way (two pole)
• intermediate
• double pole.

Different manufactures provide slightly different configurations for the terminals on the switches, but operationally they are the same. The following diagrams show the configuration of the switch and terminals as well as the switch operation.

 

One way

The 'one way' switch makes contact in one position only. It is used to open or close a single electrical circuit. In the 'on' position the contacts make a connection between C (common) and terminal one. The switch may have one or two additional terminals for looping.

 

 

Two way

The two way switch makes contact between a common point and either of two other contacts. This is commonly used for two way switching a light, or could be used to supply power to either of two circuits. A fourth terminal is supplied for looping.

 

The two way switch can be used as a one way switch, by using only one section (terminal 2 left blank).

Intermediate

The intermediate switch has no 'off' position. It is a four terminal switch that provides a path between two active wires and two load wires. When the switch position is changed, the supply is crossed over. This switch is used in conjunction with two way switches to provide three or more switches for one lighting circuit. There is no looping terminal.

There are two different diagrams used to represent intermediate switches.

The first is shown in the diagram below.

 

The below diagram can also be used to represent the movement of an intermediate switch.

 

 

 

Double pole

This is like two one way switches in the one unit operated by the one mechanism. It has four terminals and is used for opening or closing two separate circuits at the same time. There are are two separate active terminals that make or break between two separate load terminals. There is no looping terminal.