The two-gang switch is very important element to adjust the level of lighting in an apartment or private house. The light bulbs can be arranged in groups or one at a time, and the light can be supplied to them by a separate key.
Very often during repairs when carrying out new wiring, the question arises of how to connect a two-key switch to provide several lighting modes. How to connect two-gang switch taking into account the necessary safety measures - read on!
The design of the two-key switch is quite simple. It consists of:
Rarely, the third element - terminal blocks - can be replaced in the design with screw terminals. The difference is that the former hold the wire for a long time and securely, and the latter do the same, but not by pinching the wire, but by twisting it, so the first option is easier to connect and lasts longer. The design may also include additional lighting - a dimmer located on each key. Read below about connecting a two-key switch with dimmers.
Inside the two-key switch without backlight there are two wires running parallel to each other and an input for the phase. Each of the terminals suitable for the keys can, independently of the other, open or close the contact, as a result of which one lamp (part of the lamps), the second lamp, or all the lamps together turn on
.
Note! If you need to supply current not to one, but to several light bulbs at once. It is imperative to use stranded wires. This is exactly what the two-key switch model allows you to do.
The principle of operation of the switch is to vary the degree of illumination:
By the way, some two-key switches consist of two single-key devices isolated from each other. In this case, it is customary to call them modular.
In addition to the external component, such a device can also perform the functions of saving energy and creating a varied atmosphere. Two-button switches also increase safety, since when they are installed in a room, the number of points with electrical voltage is reduced.
Before starting work on preparing to connect the switch, we suggest that you familiarize yourself with the diagram of the two-key switch below:
When working with electrical equipment, extreme precision and caution must be observed, therefore all materials and tools needed for the work must be prepared and purchased in advance:
Attention! It is very important to turn off the power supply before starting work!
It is extremely important (especially for non-professionals) to correctly draw the connection diagram and lay out the wiring in advance.
The circuit should include the following three wires:
You can install the wiring in one of two ways: possible ways: open or closed. For the first you will need Additional materials- corrugated pipes or grooves, for the second - you need to make grooves in the walls.
Please note that wiring is done before plastering the walls and ceiling. This means that only after all the wires have been laid and are sufficiently insulated, you can begin finishing work.
To make a small recess under the switch, you will also have to use a chisel and a hammer (this is not necessary if the switch will be installed in the old place).
Before making the connection, you must first strip the ends of the wires by 1-1.5 centimeters to ensure good contact with the terminals. If the wires are powerful, multi-core, at this stage you need to press off their ends.
A switch with two keys should have three wires. One of them is input - phase, and the other two are output, which will supply voltage directly to the lamp itself.
The neutral wire and grounding, as already mentioned, are connected directly to the light source (to the light bulbs, or more precisely to their contacts).
After this, you need to find the phase wire and the entrance to it (unlike the outputs, there is only one). Look at the switch, previously freed from the top casing. At least one arrow must be drawn on it. It usually indicates where the phase will come from and where it will go. Near the base of the arrow, the phase wire should have an entrance.
As a rule, in such switches the terminals for the phase input are marked with the symbol “L”, in turn, the terminals for the output cables are marked with arrow symbols.
To accurately find the phase, use a special device. And if it is not there, you can determine this experimentally by temporarily connecting a chandelier or lamp.
So, you need to alternately connect one wire with pliers in pairs (not simultaneously!) to two others. That is, you select one wire and connect it first to one of the remaining ones, then to the other. This wire, from which first one or another group of lamps (luminaires) will light up, is the phase.
When a phase is found, it can be connected to the input of the switch (this is the first wire that goes to the switch), and the other two wires - to the two output terminals, respectively (these are the second and third wires that go to the switch). Next, all that remains is to insulate dangerous places on the wires and insert the structure into the socket box, which should be screwed to a place previously prepared for this.
Afterwards, all that remains is to install the accessories and you can check the device in operation.
To better understand the connection diagram, we suggest watching the video below, which describes in detail and shows examples of the connection diagram of a two-key switch:
The backlit switch makes small additions to the circuit described above. Namely: two more wires appear (so that when the light is turned off, a red indicator on each of the two keys lights up - this makes it easier to find the switch in the dark).
So these extra wires come from the mini LEDs located on the keys. Next, you need to connect one of them to the phase that goes from above, and the second, which comes from below, to the wire that goes to one of the two lamps (groups of lamps).
Connecting a switch that controls the light with two keys is not difficult if you strictly follow the instructions given above. Read all instructions first and useful tips so as not to miss anything, then everything will work out!
Light switches are one of the most common electrical installation products. Every apartment, house, office has at least a few of them. To save space and reduce the amount of work, switches can have not one key, but two or even three. But double ones are still more popular. That’s why we’ll talk further about dual (with two buttons) switches. They are also called two-key, two-button, double, etc. Connecting a double switch is quite possible for a novice electrician. Even without special skills, you can handle this yourself.
If you need to connect two light bulbs or two groups of lamps, and it is necessary for them to turn on independently of each other, you need a two-key switch. They are very easy to distinguish - two buttons are installed in one housing. By the way, the presence or absence of backlight does not affect the connection in any way. Neither the schemes nor the principles change.
The circuit of a two-key switch is simple: these are two normally open contacts, each of which is controlled by its own button. This means that in the initial state no current flows through the switch, since the contacts are open. By pressing the key, we close the contacts, the lights light up. This is the operating principle of any switch. The two-key one differs only in that it has two groups of contacts.
If you look at the design of a two-button switch, we see that it has one input and two outputs. The phase is connected to the input of the switch, and the wires that go to the light bulbs/chandelier are connected to the output.
Connecting a double switch yourself is not difficult. You can cope even without special knowledge and skills. But you have to be extremely careful - it's still electricity. We must follow safety precautions. Things to remember:
The easiest way to check is to use an indicator screwdriver. If you touch a live wire with it, the signal light on it will light up. This is how the phase is determined. If the light does not light, it is the neutral or the wires coming from the light bulbs/chandelier. Only after understanding all the wires can you begin to connect the two-key switch.
When connecting the switch, remember that the phase that comes from the panel is supplied to its input. This is the basic rule. This is the only way the connection will be correct. The phase is taken in the distribution box, which is usually located above the switch (sometimes, with lower wiring, below it) in the distribution box.
Please note that work is carried out with the voltage turned off. If there is a circuit breaker through which the lighting is powered, turn it off. If the wiring is old, unscrew the plugs. Before work, make sure that there is no voltage on the wires (touch all with an indicator screwdriver).
Most often, two loads are connected to a two-key switch - one light bulb or a group of lamps. In any case, the scheme will be the same.
A phase wire is connected to the input of the switch. The contact at the top of the switch is loosened (turn the bolt a couple of turns counterclockwise), the wire stripped of insulation is inserted along the plate (stripping 4-6 mm), the mounting screw is tightened. When tightening the bolt, apply considerable force. You can check whether the wire is securely fastened by tugging it well a couple of times. If you can't get it, everything is fine.
In the same way, connect two wires that were sewn from light bulbs/chandeliers. The contacts to which you need to connect are located below. The principle is the same - loosen the screw, insert the wire, tighten it, pull it.
It doesn’t matter where to connect which wire (to the right or left contact). It just depends on which key will turn on which light bulb. If desired, they can be swapped later.
After the connection is completed, install the keys, turn on the power, and check the operation of the switch. If everything is done correctly, there should be no problems.
In addition to just switches with two keys, there are blocks with a socket. In this case, the connection of the double switch does not change, but a zero and grounding must be added to the socket.
So, we supply a phase to the block of switches, and from the output of the switches the phase goes to the light bulbs. We supply a phase to the socket block (you can take it from the entrance to the switch block), set “zero” to the second contact - from the corresponding bus on the panel. We connect the ground to a special ground contact.
In the double switch connection diagram described above, three wires are needed - a phase from the distribution cabinet and two wires from the light bulbs. But sometimes four or more come. What to do then?
There is a weak point in the specified algorithm - we assumed that the remaining wire is ground. Logically, this is correct. But, unfortunately, there are exceptions. Therefore, before manipulation, you should decide whether this is really “earth” in front of you. To do this, you can measure the voltage using a multimeter (set the measurement limit to 1000 V - just in case, then you can reduce it). We touch the phase one with one probe, and the nameless one with the second. If it shows 220 V or a figure close to it, this means “zero” and not “ground”. If the readings are lower than 220 V, this is “ground”.
This “measuring device” can determine the “zero” or “ground” of your unknown wire
If you don’t have a multimeter, you can use a light bulb to which you connect two wires (you can take table lamp, wrap two wires around the plug). Take single-core wires, rigid, of sufficient diameter. Their ends need to be cleaned, but you will only hold on to the insulation. We touch the phase wire with one end, and the “unknown” wire with the other. If it’s on, it’s “zero”; if it’s off and the machine is knocked out, it’s “zero.” This method is dangerous to health, so we act very carefully.
If you decide to change old switch to a new one, but not a phase, but a zero is connected to the old one - this is wrong and everything needs to be corrected urgently. The light bulbs will work, but with this connection they are always energized. In this case, even replacing a burnt-out lamp is a deadly undertaking. I'm not kidding. This is true. Therefore, if the switch is connected incorrectly (if zero comes to it), everything must be corrected. There are two options here:
If you are connecting a double switch with your own hands for the first time, it is better to double-check your actions several times and work very carefully.
Finally, let's talk about how to install switches. It doesn’t matter how many keys they are. The sequence of work is the same:
This completes the installation and connection of the double switch. You can check your work.
We connect a two-key light switch at home
There are many applications for double switches. They are usually connected to chandeliers in order to be able to adjust the lighting intensity: turn on a certain group of lamps, one lamp, or all at the same time. Another common application: lighting separate bathrooms or connecting a hood and lighting.
In private homes, a switch with two keys often turns on the lighting outside at the entrance or inside in the hallway. Where lighting is provided to the balcony or loggia, double switch It would also be appropriate not to install 2 separate switches in the room for each zone. Zoning rooms using lighting or design accents is becoming increasingly popular, and double switches are also often used to implement such tasks.
Connecting objects to a switch with two keys is quite within the capabilities of the average business person. This does not require supernatural knowledge and skills. All you need is to have certain equipment and understand all stages of the work.
What you need to know before connecting a double light switch
First you need to check the wires, that is, test which one is phase. Using an indicator screwdriver it is not difficult to do this: upon contact with a phase in the screwdriver, the signal LED will light up. Mark the wire so that when performing further operations you do not confuse it with the neutral one.
Before you begin installing the switch, you must secure your work area.
If we're talking about about the chandelier - you should turn off the power to the wires coming out of the ceiling. When the type of wires has been determined and marked, you can turn off the power (to do this, use the appropriate circuit breaker in the panel) and begin work on installing a double switch.
Decide in advance and ensure that you have connecting material for the wires. Typically used:
The most convenient and reliable way– fixation with self-clamping terminals. Screw clamps can weaken over time, and electrical tape tends to lose elasticity and dry out. Because of this, the reliability of the connection may weaken significantly over time. Self-clamping terminals provide a reliable, strong connection.
To properly connect the switch to the light bulb. You must carefully study the step-by-step instructions on how to do this. After this, you can not only make the installation according to the diagram, but also identify possible malfunctions.
When providing electrical installations in premises, the question often arises of how to lay the cable using corrugated pipe. You can find out all the tips on choosing corrugations and the sequence of work here.
To perform all operations accurately, you must have the following tools:
Preparing wires for correct installation
Depending on the type of device being connected, preparing the wires may involve various manipulations.
If you are installing a chandelier with 2 wires coming from each lamp, you can connect it according to your preferences. Modern lighting equipment often has ready-made wires already connected in a certain way. In this case, to change the options for lamp combinations, you will have to disassemble the base of the lamp. If this matters to you great importance, pay attention to the wires at the time of purchase to avoid unpleasant surprises when connecting the device.
There are usually three wires coming out of the installation box. It is necessary that their length does not exceed 10 cm. This is quite enough for comfortable work. If the wires are longer, just cut them. Next, you should strip the ends of these wires of insulation by about 1-1.5 cm and connect them to the corresponding terminals of the switch.
The phase is connected to the terminal marked “L”, and the remaining wires are connected depending on which switch key you want to use for a specific section of the lamp or individual devices.
If you have a modular type switch, that is, consisting of two separate single-key components, you must provide power to both parts. To do this, make a jumper from a small wire and install it between the two halves of the switch.
A two-key switch consists of 2 single keys assembled in one housing. The neutral and ground wires approach the sections directly, and the phase passes through the switch. Thus, when the corresponding key is activated, the circuit is broken, that is, the phase suitable for a certain section of the device or a separate device.
Connecting the switch to the distribution box is described above. It is often unclear how to carry out electrical installation at the point where the chandelier is connected to the double switch. There may be several options here, depending on whether the number of wires on the ceiling matches the number of wires coming out of the chandelier.
A common problem is that the breaker does not operate the way you expected it to. For example, when you press the first key, a certain section does not work, but when you press the second, all lamps work simultaneously. That is, there is no distribution of lamps to switch keys.
Another option: when you turn on the chandelier, only some of the lamps work, and all of them do not light up even when both switch keys are pressed.
Starting with the choice of assembly location, size, and ending with the connection of all components according to the diagram - this is the secret of how to make a Tesla transformer with your own hands. Special attention precautions should be taken in this regard.
Is it possible to connect a three-phase motor to a 220 volt network? This article will provide an opportunity to understand how high-power devices operate in single-phase networks.
And finally, the saddest option: the switch does not work at all.
Most likely, when connecting, you did not match certain wires and connected them in the wrong order. Perhaps you neglected to check the wires on the ceiling and in the junction box, and relied only on the colors and markings. And in no case should you do this, since when installing wiring, non-compliance with marking standards is very common.
In order to find the reason, you need to go back to the beginning of the installation and carefully follow all the steps.
Armed with an indicator, be sure to ring all the wires and label them. If you suspect a wire malfunction, contact a specialist. If there are no problems with the wiring, re-fasten the marked wires according to the diagram and be extremely careful.
Thus, you should follow simple recommendations so as not to encounter problems when performing electrical work:
Video on the installation diagram of a double switch
For more detailed information on how to connect a two-key switch, we recommend watching the video:
How to connect a switch with two keys? Detailed diagram connections
Two-key models are widespread and are installed on almost all buildings and structures for domestic and industrial purposes. Switches of this type provide control of light from one place in different rooms. Turn on the light on chandeliers with two groups of lamps or two groups of lamps in large rooms. The connection diagram for a two-key switch is not so complicated, but in order to assemble the circuit and correctly install all the elements, you need to be thoroughly familiar with the details of this process.
Design features of a two-key switch
Like all products, two-key products are divided according to the following criteria:
Two-button switch for hidden wiring
For what type of wiring is used, external or hidden, the difference between the housing design and installation methods. For internal wiring, the housing has a mechanism of sliding strips that fix the switch inside the wall hole. Sockets for fastening products on the walls are made using perforators with a crown with pobedit or diamond cutters. First, a plastic or metal cylindrical socket box is installed, then the housing structure. By rotating the screws of the spacer mechanism, the strips extend, they rest on the opposite edges of the mounting hole, rigidly fixing the housing of the hidden wiring light switch to the wall. Products for open wiring are more often used for buildings with wooden walls or in prefabricated panel structures. The housing is attached with self-tapping screws to the wall surface.
Two-key light switches differ in the type of contacts; two types of contact designs are used. Screw-type, the bare end of the wire is clamped with a screw between two metal plates. A very reliable method, but it has one significant drawback: if the wire is loosely clamped or the wire cross-section is incorrectly selected, the contacts heat up.
This leads to a weakening of the clamping force; it is necessary to periodically tighten the screws. Otherwise, there will be a complete loss of contact or fire of wiring, other plastic elements light switch. In the clamping design, the end of the wire is fixed by a plate, which is constantly pressed by a spring, ensuring stable contact.
Light switches can be divided according to the material from which the housing is made, plastic or ceramic. They must be marked with the permissible value of current, power, volts. Ceramic products dissipate heat well and are designed for installation in circuits high loads 10A, 220V, power up to 2300W. Plastic cases are designed for lower currents of 3-6A.
Criteria for choosing a two-pole switch and other circuit elements
Before choosing a suitable sample and assembling the circuit, decide on the network parameters, what kind of wiring will be, hidden or external. How much power the lighting fixtures will consume; use the current strength to determine the required wire cross-section. For a chandelier with two groups of lamps, one 100 W and three 40 W, the power consumption will be P = 220 W. We calculate the current:
With such a load, it will be enough to install a two-key element with a plastic case for 3A, wire cross-section 0.75 mm/sq.
When you need to illuminate a sports hall, where there are two groups of eight lamps, each lamp has 3 lamps daylight 80 W each. Power of one group P = (80 x 3 x 8) = 1920 W.
I = P/U = 1920W/220V = 8.7 A.
For such a lighting circuit, you will need to install a two-key switch in a ceramic housing with a permissible load current of 10A. The cross-section of the wire is selected according to pre-calculated tables, they are in the PUE (Electrical Installation Rules).
To save on electricity bills, our readers recommend the “Electricity Saving Box”. Monthly payments will be 30-50% less than they were before using the saver. It removes the reactive component from the network, resulting in a reduction in load and, as a consequence, current consumption. Electrical appliances consume less electricity and costs are reduced.
As practice shows, in most cases a three-core cable with copper wires 0.75 – 1.5 sq./mm.
The most affordable and frequently used cable brands:
Design and principle of operation of a two-key switch
This is a mechanical design, with three contacts, one fixed (common) and two independent from each other. When you press the corresponding keys, the brass plates are transferred to the common contact, completing the circuit. Two-key designs have 6 operating positions:
Thus, the lighting groups connected to the two-key switch are controlled. They can work simultaneously when both keys are turned on or separately when one of them is turned on.
Connection diagram for two-button switch
When connecting to one lighting device (chandelier with two groups of lamps), three cables with three copper wires are inserted into the distribution box:
Connection diagram for two-button switch
The blue wire is directly connected to the zero contact of the chandelier. Red comes to the fixed (common) contact of the switch, the yellow-green wire is connected to the ground terminal of the lighting fixture. The two remaining movable (output) contacts are connected through the box to the free terminals of the lamps. If two lamps are connected for different rooms, the lighting is controlled by a two-button switch, four cables are connected to the box:
The connection principle does not change; the yellow-green ground wires of the housings are connected into one contact. Next, it goes to the grounding bus of the distribution board. Unused wires can be insulated and left as backup.
Please note that the requirements of the rules for the color of insulation and the purpose of the wires can be fully met only in two sections of the circuit. Cable from the distribution board to the box and from the lighting fixture to the distribution box. From the output contacts from the switching point to the box, these requirements cannot be met; wires of any color can be used. In this case, you need to be very careful, especially with hidden wiring.
To check, use a multimeter in dial mode or other measuring instruments. The phase (red wire) always opens in the lighting circuit. This is done primarily for safety when repairing lamps or installing new ones. When you turn on the circuit breaker on the distribution board, you can easily check the presence of a phase using an indicator screwdriver. Then on lighting fixtures You can check the phase by making sure that the two-pole switch is working properly.
Features of wall mounting
In reinforced concrete and brick buildings recommended for lighting hidden wiring, distribution boxes and switches should be placed in pre-prepared slots. It is better to insert plastic socket boxes with holes for mounting screws and fix them with plaster mortar.
For reliable fastening, buy two-key products with a design that provides two fastening methods:
The housing, fixed to the spacer mechanism and screws, will never fall out of the wall.
Two-button switches for external wiring are simply screwed to the wall, and distribution boxes are also attached. It is advisable to lay the wires between them in plastic cable ducts.
Knowing design features, products for hidden and external wiring, how to assemble a two-key switch connection diagram, principles of operation of the control circuit, it will be easier for you to do right choice necessary elements. Knowledge of how to connect a two-key switch makes it possible to install all the elements of the circuit without resorting to the services of electricians.
How to properly connect a light switch
In this article you will learn how to properly install a light switch. Switches are used to control electrical lighting sources in residential and commercial settings. In most cases, switches are wall mounted. The location, height at which they are installed, and the shape of the switches vary from country to country. Switches come in various types: single- or multi-key, for installation indoors or under open air etc. Installing and wiring a switch is not a difficult task, provided you understand the basic principles of electrical networks and follow safety precautions when carrying out electrical work.
In this article, we will show you step by step how to install a switch. For this you will need:
Preparatory work
The first thing you should do is turn off the power. Some people believe that it is enough to turn off only the circuit on which the breaker is to be installed, but we strongly recommend that you completely turn off the power to your apartment.
Use a voltage indicator on each wire to make sure it is safe to touch them. It's better to check several times before starting work.
The next step of the project is to clean the electrical outlet (installation box) from paint, small pieces of drywall, dust and dirt. This operation is very important, especially if we are talking about a newly renovated room or apartment in a new building. But even if you're replacing an old breaker, it's best to assess the condition of the socket box beforehand to make sure the new breaker can be installed and aligned properly.
Preparing the socket box for installing the switch.
Once you have purchased a new switch, you must disassemble it using a screwdriver or simply by hand, depending on its type and manufacturer. This operation is not necessary, since you will be connecting electrical wires to the inside of the switch. It is necessary to remove the switch buttons and frame.
Now you have to connect the wiring. Using pliers, cut off the excess length of the wires - they should protrude from the wall by about 15 cm. This length should be enough to connect the switch without much difficulty. The wires should not be left too long, otherwise they will be difficult to place inside the socket box.
Once you have cut the wires to the desired length, you can proceed to the next step. Using pliers, strip about 2 cm of insulation from each wire. Stripping a long length is dangerous, since exposed wires may accidentally come into contact during operation, causing a short circuit.
Use pliers to shape the end of each wire into an L-shape (or C-shape for some switches with side screws).
Advice: the simplest and effective method strip the wire - use special pliers to remove the insulation.
Removing insulation from wires.
Connecting wires to the light switch
You probably noticed that the wires are colored differently: the brown wire is the phase, the yellow-green wire is the ground. (Color-coded conductor insulation standards vary from country to country.) Each of these wires must be connected to a specific terminal.
How to properly connect the switch? There are slight differences in the connection of one- and two-key switches. The main thing to remember is that the phase must open; the phase wire is attached to the connector marked L (usually at the bottom of the switch).
After you place the end of each wire into its connector, secure them with screws, using a screwdriver for this purpose. Make sure the wires are secure or the switch will not work properly.
Connecting wires to the switch.
Once again, make sure that the wires are connected correctly and that they are securely fastened. In the picture below you can see how to wire a two-button light switch.
How to connect a switch with two keys.
Once you've completed connecting the wires, you should bend them to "hide" them in the box. Make sure there is enough space left to place the switch. If there are no problems, you can secure the switch in the box with screws. Take your time to tighten the screws, you should first check how well the switch is aligned.
Placement of the switch in the box.
Use a laser or spirit level to level the switch. In the picture below you can see the technique for performing this operation.
If you notice a horizontal deviation, loosen the screws and adjust the position of the switch.
Finally, do not forget to securely secure the switch with screws. Just don't overdo it, or you risk stripping the screw threads or damaging the switch.
The next step is to reattach the frame and switch buttons. You don't need tools for this, just your fingers. A slight pressure, and the elements removed at the very beginning are back in their places.
This operation is perhaps the easiest. In addition, it foreshadows the imminent completion of work.
Installation of switch buttons.
To increase the level of comfort when using lamps, a diagram for connecting a pass-through switch from 2 places will be useful. In practice, if necessary, a larger number of control points are used. To save time and money, work operations are performed independently. A thorough comparative analysis, taking into account the features of products from different manufacturers, helps to make the right choice when purchasing. These and other practical problems will be easier to solve after studying this article.
A superficial study of the problem will not allow you to draw the right conclusion. To some, such devices seem unnecessary. However, similar arguments can be made against the use of remote controls. remote control, other devices to increase the level of comfort. Meanwhile, the transition switch is not only intended for convenience. What it is is shown in the following figure:
The first picture shows a typical situation. One lamp is sufficient to illuminate a flight of stairs. It is turned on from the lower platform. Having risen to the upper platform (Picture No. 2), the electrical circuit is opened. This action is performed using another switch. When moving in the opposite direction, a similar algorithm of actions is used.
It is clear that such solutions significantly increase the level of security. They are used not only on stairs, but also in long corridors. Good lighting is especially important when there are turns, furniture, and other obstacles along the route. Such equipment is necessary if there are no windows. Modern users will be reminded of the presence of devices that perform similar functions using motion sensors and sounds.
A careful comparison with a pass-through switch will reveal the following disadvantages:
The listed arguments are sufficient for correct conclusions. Without diminishing the importance of modern solutions, it should be noted the real advantages of cheap, reliable and durable walk-through switches. Separately, it should be noted that the ergonomic indicators of residential premises are improved with the help of these relatively simple electrical products. 
Single key switch 
Pass-through switches (1 and 2) in the lighting lamp control circuit from two places
The above diagrams explain how a switch is different from a switch. The first one breaks and connects an electrical circuit. The second one changes the path of electric current.
Disassembled switching unit
This photo with explanations will help you study the design of pass-through switches. To connect the wires, screw terminals (1.3) are installed here. A complex-shaped rocker arm (2) is installed in the recesses of the support platform (4), which ensures reliable fixation. But it remains possible to swing it using the transition element (6) installed in the cover (5). If you click on it top part– the corresponding contacts will be closed, the current will flow along the path from the rocker arm through the clamp (2-1). After pressing down, a short circuit will occur electrical circuit 2-3.
Developers use different solutions, but the principle of operation of products of this group is as described above. The following explanations should be given for the given parts of the structure:
Features of modern walk-through switches
Discussed above central block installed in a metal frame (6). This design uses special latches (4) for reliable fixation and speeds up installation operations. Other models use screw fastenings. Cutouts (1) in the frame make it easy to accurately position switches, sockets and other electrical devices in one unit horizontally/vertically.
When the screws (3) are tightened, special “legs” move out to the sides. They ensure that the pass-through switch is secured in the installation box. In this model, plate clamps (2) are installed, into which conductors stripped of insulation are inserted. High-quality contact is created without special tools and additional fasteners. This modification is equipped with built-in lighting. The light bulb is installed in such a way that replacement is possible without dismantling the entire mechanism. 
A conventional device (1) and an illuminated switch (2) are connected to the circuit according to the same circuit
However, the second option ensures good visibility of the device in darkened rooms. It should be noted that this solution is not compatible with all types of lamps. When turned off, a small current passes through them. This will be enough to power the LEDs. Incandescent lamps and gas-discharge devices can be connected to such circuits without restrictions.
Protected devices with sealed gaskets are installed in an open space. They perform their functions safely in pouring rain. Built-in lighting is useful in a dark corridor. Accurate specifications selected taking into account the actual conditions of future operation. However, in any case, information on how to correctly connect a pass-through switch with a certain number of keys will be useful. It is this parameter that largely determines functionality switching device.
Schematic diagram of electrical circuits
The figure shows that the wiring is made of a three-core cable. This is necessary to connect the ground (green wire) to metal case lamp (3). The diagram shows the distribution cabinet (1). A three-wire circuit also goes from the box (2) to the pass-through single-key switches. There is no grounding provided here. 
Lamp control circuits from two and three places
In the second option, it is necessary to use a single-key cross switch (marked with an arrow in the figure). Please note that it has two switching groups, which are driven by one drive. Such products do not differ in appearance from standard switches, but they perform different functions. 
This designation is used to mark a cross switch on the housing.
According to this scheme, two-key pass-through switches are used in practice
This option makes the project more complicated. It is necessary to use cables with big amount conductors. But it is precisely the connection of a pass-through double switch that allows you to organize control of several groups of lamps. Such solutions are used in large rooms to adjust the general light chandelier. 
This figure shows how to connect a double pass-through switch in combination with a single-gang switch.
Control of three groups of luminaires 
When choosing a pass-through triple switch, the connection diagram in the manufacturer's accompanying documentation will help you install the jumpers correctly
Careful planning will prevent annoying mistakes and simplify the right choice. It is necessary to carefully determine the lighting application modes in order to accurately determine the purpose of the project. The locations of walk-through switches are established not only in accordance with current rules. The physiological characteristics of users are essential. During the comparative analysis, they take into account appearance and functionality, prices and manufacturer warranties. An integrated approach will help to implement plans of any level of complexity without extra costs.
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The double switch for a 220 volt network has a similar internal organization with the classic single-key model. In essence, such a mechanism is two combined single-key devices. Correct connection it won’t take much time, you just need to understand all the nuances of the correct connection of the conductors.
So, first you need to buy everything you need. Namely: a switch with two keys, a mounting box (if produced internal installation into the wall), three-wire cable, set of terminal blocks.
Three variants of circuits - all identical in function
In their apartments they use a two-button switch to connect a chandelier with several bulbs or spotlights on the ceiling. One group of spotlights or lamps in a chandelier is controlled by one key, the second group by another. The number of spotlights or chandelier bulbs in each group can be from 1 to ten.
If one lamp is located in the corridor, and the second is in another room, there will be more outgoing wires, since each group will have its own wire or cable. The connection diagram will take a different form:
From the apartment electrical panel, power comes to the distribution box in the form of two wires: phase (red) and zero ( of blue color).
It is the phase and not the zero that is placed in the gap, that is, on the switch, because this method is the safest. When turning off the power, turning the switch to the “off” position, it would be correct if there is no voltage left on the lamp socket, and when connecting the zero to the gap, this is exactly what will happen, and simply replacing a burnt-out lamp can turn into every second exposure to the danger of electric shock.
The installation of a double type of switch should be carried out exclusively in a socket box, the diagonal of which is 67 mm. The old-style socket boxes have a diagonal of 70 mm, since the old devices were larger and do not fit well under modern models. In addition, they used to be made of metal, not plastic. And don’t forget to use cables of the required diameter, which was described in detail in the link.
