What is Intermediate Switch – Its Construction, Working & Uses in Electrical Wiring

Intermediate Switch, Construction, Operation & Applications

What is Intermediate Switch & How it Works?

It is a very useful switch with four terminal and commonly used when we need to control a light point (or any other electrical appliances like fan, alarm, in the middle of stair etc) from three different places.

It is also known as 4 way switch in US as well.

Construction & Working of Intermediate Switch

In an intermediate switch, there are four terminals by which it changes the flowing of electric current from one circuit to another (see fig 1 & 2) and also known as three way switch. It has the ability to ON and OFF the electric supply by two ways. The four terminals of intermediate switch construction and its operation are shown in fig below where the 4 contact points may be known as A, B, C & D. When the switch knob is up, the terminal contacts of intermediate switch connect terminal A with terminal C and terminal B with terminal D as shown in fig 1a. On the other hand when knob is down, terminal A is connected to terminal B and C to D then.

in other words, When the knob of the switch is UP, then the vertical contacts are connects in such a way like AC and BD as shown in fig 1a). And when the knob is DOWN, then the Horizontal contacts are connected (i.e. AB and CD as shown in fig 1b).

Fig 2 shows the basic construction and working of Intermediate switch.

• Related Electrical Wiring Tutorial: Staircase Wiring Circuit Diagram – How to Control a Lamp from 2 Places (2-Way Light Switch) ?

Application and Uses of Intermediate Switch

Intermediate switch is mostly used in a hall, big rooms or godown where different lamps are needed to ON/OFF from different places. Moreover, in a multistory building, the lamp at ground floor or in car parking shade can be controlled or ON / OFF from any floor by using intermediate switch circuit.

How to Control Light Point from Three Places using Intermediate Switch

In Fig 3, a lamp is controlled from three different places by using two, 2-way switches and one intermediate switch.             

Below is the same diagram (Fig 4) to control a light point (lamp) from three different places by using two, two-way switches  and one intermediate switch with different symbols.

Staircase Wiring using Intermediate Switch

Below is a given schematic circuit to control a light point from three different places by using two 2-way switches and intermediate switch in the middle of stairs.

Controlling of Lamp from 6 Six Places by Intermediate Switch

In fig 5, a lamp is controlled from six different places by using two, 2-way switches and four intermediate switches.

Key Point: You may control a lamp from many different places by adding more intermediate switches such as in the middle of stair or in shared flats (when needed). Also, many other electrical appliances like fans, alarms, machines etc can be control from different places by using intermediate switch.

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