In building wiring, it is important to have an effective and flexible control of the electric lighting system. Irrespective to the type and purpose of the premises, the lighting controls in the building marks the beginning of the efficient use of energy.

For example in staircase, the efficient use of energy starts with the conventional control that enables a person to control the light whether he is in the upper floor or in the lower floor. A person can switch ON the light as soon as he climb the stairs and then he can also switch it OFF when he is already in the upper floor.

 Staircase

The same thing happened in the long hallway, there must be a means where the occupant can switch ON and OFF the lights at any strategic point along the hallway.

 Long Hallway

And so how can we make it possible?

This article covers only the conventional method, without the use of building automation system.

Controlling the light in two locations

Type of switch needed:

• 2 units of 2-way switch (called 3-way switch in North America).

 Terminals of 2-way switch

As we can see the 2 way switch has 3 terminals namely L1, L2 and common. The connection of the circuit can be done using the following steps:
1. From the source, connect the LINE/HOT conductor to the common terminal of the first switch.
2. From the LINE terminal of the light, use conductor to connect it to the COMMON terminal of second 2- way switch.
3. Connect L1 of the first switch to L1 of the second switch.
4. Connect L2 of the first switch to L2 of the second switch.

This can be best demonstrated in the diagram below,

 Light controlled in 2 locations

Controlling the lighting circuit in 3 or more locations

Type of switch needed:
• 2 units of 2-way switch (called 3-way switch in North America).
• 1 unit - Intermediate Switch (called 4-way switch in North America).
This method can be used efficiently in long hallways where a switching point is a must in a strategic point along the hallway. Here, the use of intermediate switch (4-way switch in North America) is needed.

 Intermediate Switch

This type of switch has 4 terminals and to be installed in between 2-way switches. For example, if there is a need to control in 3 locations, the 2-way switches will be installed in each end while the intermediate switch will be installed in the middle.

If 4 locations is required then there will be 2 intermediate switch in the middle.

The connection of the circuit can be done using the following steps:
1. From the source, connect the LINE/HOT conductor to the common of the first 2-way switch.
2. From the LINE/HOT terminal of the light, connect it to the common terminal of the second 2-way switch which is to be installed in the other end of the circuit.
3. Connect the intermediate switch in the middle.
This can be best demonstrated in the diagram below,

 Light Controlled in 3 locations.

Note that the 1- unit intermediate switch is just a minimum.  In case the requirement is controlling light in 4 locations, then 2 units intermediate switch are needed.

In general, we need to understand that the Intermediate Switch is always installed in the middle no matter how many units are required. The 2-way switch on the other hand need to be installed in both ends of the circuit.

This can be further explained in the diagram below,

 Light Controlled in 4 locations.

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