Two-way switches are used when we need to switch on and off a lamp from two places. This switch is also called switch „scheme 6“, unlike the ordinary light switch, which is called key „scheme 1“. Examples of the use of two-way switches are hallways, stairs or bedrooms – you turn on the lights when you enter the hallway and turn them off at the end of the hallway when you leave; or – you enter the bedroom and turn on the lamp from a switch located next to the door, then you go to bed and turn off lamp from a switch located next to your bed.
When we have schemes with two-way switches each of the switches has three conductors while ordinary switches have two conductors. The phase conductor goes into the first two-way switch together with two conductors connecting it to the second two-way switch. The two conductors from the first switch go into the second two-way switch. A phase conductor goes out of the second two-way switch towards the lamp.
The neutral conductor from the supply chain goes directly to the lamp. If the hallway or stairway is long, more than one lamp can be placed in parallel to the first one.
Things like logic and circuit are quite simple, so we will focus on the practical connection of the switches and the lamp, i.e. the assembly. Let us assume that we have two cantilevered boxes at either end of a hallway which have three conductors each. First we need to put down the safety device and strip all the wires, being careful that they don’t get in contact. Then we switch on the current and look for a phase by means of a phase-meter. We should find phase only in one of the conductors. We mark the conductor for example with red tape and again put down the safety device. We take one two-way switch and connect the phase on the side of the common terminal.
There are two terminals on the other side of the switch. Two power conductors need to go out of these terminals to the second switch, where they go into its two terminals and the conductor which supplies the consumer, respectively the lamp, is connected to the side of the common terminal. This conductor is phase for the lamp. We also need to take a neutral conductor to the lamp. This is briefly how you connect a lamp to two two-way switches.
Sometimes the light source needs to be operated from three places. Then we have to use switch „scheme 8“, also called “cross switch”. It functions as two two-way switches in a common housing and a common managing switch. Schematically the cross-switch is placed between the two two-way switches, and its function is to „reverse” the two conductors. The cross switch must have bridges placed crosswise between the terminals.
The schemes also show simpler connections with an ordinary light switch – switch „sheme 1“ as well as a series switch „scheme 5“. The series switch is used to connect a different number of lamps to a chandelier, for example. One of the buttons switches on two lamps, and the other one – three more lamps. These are the most used schemes for connecting the lighting in a building. In practice, it is often necessary to use junction boxes, where actually the connection according to a chosen scheme is realized. Many manufacturers of light switches put their product in a wiring diagram and even add photos of ways how to connect the switches.
It is important to note that switches sheme 1, sheme 6 and scheme 8 look the same, at least their front side, so when buying it is important to specify what switch we need and to check its rear side. Another type of light switch is the so called light button, used for the lighting of stairs. Unlike two-way and other types of switches, light buttons have only one stable position. This means that when pressed, after all stair lights or some of them are turned on, it returns to its initial position. The lights are turned off by a timer located in the staircase machine.