How a 2 Way Switch Wiring Works? | Two-Wire and Three-Wire Control

In this tutorial, we will learn about a simple however interesting concept called the 2 Way Switch. It is besides called as a Staircase Switch, as you can control a single load, a light bulb for case, from two unlike places, like either ends of a stairway .
WARNING: This is fair a hypothesis explaining how a distinctive 2 Way Switch wire works. It is not an drug user guide on how to install or wire a 2-way switch. If you are planning to implement a alike setup in your home, then decidedly consult a professional as the process involves working with 230V AC Supply ( or 110V AC, depending on where you live ) .


We use switches all the time in our homes, offices, cars, industries and many other places. The gadgets we use day by day ( fluid call and laptop ) consists of several switches. A Switch is an electric device which is used to open or close an electric circuit .
There are different types of switches : Toggle Switch, Momentary Switch, Rocker Switch, Digital Switch, etc. All the switches perform elementary job of either interrupting the flow of electric current or divert the menstruation of current. They basically ‘ make ’ or ‘ break ’ the circuit.

All the switches we use regularly to turn on or off lights, fans, etc. are two terminal devices. But there is a limited switch called ‘ Two Way Switch ’, which is the an significant component in the implementation of Staircase Lighting .
indeed, before proceeding to learn about the cable of a 2 way trade, we will learn about the Two-Way Light Switch, which is the main chemical element of the 2 Way Switching, regardless of the type of wire used. It is a standard single perch double project interchange with three terminals .
The three terminals are normally named COM, L1 and L2, but sometimes the terms COM, 1 Way and 2 Way are besides used. In one position, the COM and L1 terminals are connected, while in the irregular position, the COM and L2 terminals are connected .
This type of connection is typically called a “ Break before make ” invention, as the first joining has to be broken before making the moment connection. This is in contrast to a even two terminal switch, which is just a make or break device .
The surveil picture shows the front and back view of a distinctive family two-way switch .
Two-way Light Switch

How to Wire a 2 Way Switch?

As I have already mentioned in the presentation paragraph, a two way switch is identical utilitarian in stairway ignite as you can turn on the light just before you start to climb the stairs and once you reach upstairs, you can turn off the light up simply by toggling the interchange placed near the clear of the stairway .
There are a couple of ways in which you can make a bipartisan throw joining. One is an older method, which is not often used now-a-days and the other is a more modern and safer version, which is being implemented in industrial ampere well as residential applications. Let us take a count at both these wirings .

Standard 2 Way Switch Wiring

The first manner of wire uses a copulate of Two-Way Light Switches with a three wire control ( 3 Wire Control ). The succeed is the simple schematic of a three-wire 2-Way Switch wire .
Standard 2 Way Switch 3 Wire Method
You can observe in the schematic that both the COM terminals are connected together. The L1 terminals of both the switches are connected to wrinkle ( or phase or live ) of the AC Supply .
The L2 terminals of both the switches are connected to one terminal of the light bulb, while the early terminal of the light bulb is connected to the neutral of the AC office add .
From the schematic, you can easily visualize how the cable works. In the default state shown in the above effigy, the alight is off. If either of the switches is toggled, the light turns on. To turn off the light, you can toggle any interchange .
For case, in the above state, the COM terminals of both the switches are connected to respective L1 terminals. now, if we toggle Switch 1 i, COM of Switch 1 is now connected to its L2 terminal, then there is a path to complete the tour and the light turns on .
To turn off the unaccented, we can toggle either Switch 1 or Switch 2 as any toggling action will break the run of current to the abstemious. so, considering all the possibilities, the light is on in two cases :

  • COM of Switch 1 is connected to L1 and COM of Switch is connected to L2.
  • COM of Switch 1 is connected to L2 and COM of Switch is connected to L1.

If we compare this frame-up with digital electronics, then this is like to an Ex-OR Gate, where the condition of the light ( ON or OFF ) depends on the status of the COM terminals of both the switches connected to respective L1 and L2 terminals .
The following table shows the truth board for Standard Wiring i, 3-Wire Control of Two Way Switch, where the output ( status of the light ) depends on what terminal ( L1 or L2 ) is connected to the COM terminal.

Switch 1 COM (connected to) Switch 2 COM (connected to) Status of Light
L1 L2 ON
L2 L1 ON

This method is recommended as both the course and neutral wires come from the same lighting tour ( or breaker ) even though it uses more telegram .

Alternative Method of Two Way Switch Wiring

The future electrify blueprint is an honest-to-god system which you might find in some older homes and industrial settings. It is besides called as two wire restraint electrify ( 2 Wire Control ) .
This cable system is not recommended for mod implementations and if you are planning to install a new apparatus or replace an older one, then the previous wiring must be used .
I have included the option wire method fair as a character and I will besides explain its drawbacks .
Coming to the actual electrify, the postdate conventional shows the implementation of a two-wire control two-way substitution .
Alternative 2 Way Switch 2 Wire Method
L1 terminals of both the switches are connected in concert and L2 terminals of both the switches are besides connected together. Coming to the COM terminals, the COM terminal of the first gear interchange is connected to phase ( or line or live ) .
The COM end of the second switch is connected to one end of the light bulb while the other end of the lighter bulb is connected to the inert of the AC Supply .
In the default state ( as shown in the conventional ), the sparkle is off. But when either of the switches is toggled, then the light turns on. In terms of digital electronics, this shape is alike to an Ex-NOR Gate .
The following postpone shows the truth mesa for Alternative Method Wiring i, 2-Wire Control of Two Way Switch

Switch 1 COM (connected to) Switch 2 COM (connected to) Status of Light
L1 L1 ON
L2 L2 ON

flush though this method acting saves cable, it is not being preferred anymore as the Phase and Neutral may come from different lighting circuits ( or breakers ) .
Another major flaw is with respect to electromagnetic interference. We know that any current transport conductor emits electromagnetic radiations. If the Live and Neutral wires are placed in close proximity, they cancel each early ’ south EM Radiation .
But in this wire, there is possibility that the neutral and hot wires are being run individually at different parts of the house, making the wires a giant generalization loop. This will decidedly cause noise problems with other EM and RF Signals .


I do not have Two-Way Light Switches to demonstrate the solve but I thought I would make a similar frame-up using a match of Single Pole Double Throw ( SPDT ) Toggle Switches and an LED ( as basically, a two way throw is an SPDT Switch ) .
The SPDT Toggle trade can be considered as a bipartisan Light Switch as it has three terminals and works very similar to the bipartisan light throw .
The succeed image shows a typical SPDT Toggle switch with its terminals.

2 Way Switch SPDT
For wire, I selected the standard way of wire ( the inaugural method i, the 3-wire control condition ) with a 3.7V Lithium-Ion Battery as the baron add. It worked flawlessly .


A accomplished founder ’ s guide on two way switch, working of two way switch wire, different types of wiring for two way throw or Staircase Wiring and besides the schematic for the wire .

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Category : Tech

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