From being used on a vacuum cleaner to being used on a life-support machine, the purpose of a switch is to open and close a circuit. A switch is used when incoming power in an electrical product design needs to be controlled. Opening a circuit (turning a device OFF) is achieved by breaking the connection. This interrupts the current flow. Closing the circuit (turning a device ON) allows the current to flow again.
On/Off Markings
A common style of a switch is a rocker design, which includes on/off markings. To meet the standard IEC 60417, the symbol for ON is “I” (a straight line) and the symbol for OFF is “O” (a circle). It is important to check the appropriate equipment standard for instructions regarding the position of “on” as some may require the “I” to be installed in a vertical position.
These on/off markings can be found on the end of the actuator or on the face of it. The actuator is the mechanical component used to manually turn a circuit on and off. “From my experience, the face is the most common and easiest to see. They can either be ink or paint marked or the marks can be molded into the actuator. The molded-in marks are harder to see,” explained Dan Ford, Technical Support Specialist atInterpower.
There are different types of switches to choose from. A switch wire or pole indicates the number of circuits that it controls. So a single-pole switch refers to one circuit and a double-pole switch refers to two circuits. A double-pole switch can be similar to two single-pole switches side-by-side.
There are four main classifications for the types of switches:
Single-pole, single-throw (SPST)
Single-pole, double-throw (SPDT)
Double-pole, single-throw (DPST)
Double-pole, double-throw (DPDT)
The double-pole, single-throw rocker design is used in switches carried by Interpower. DPST switches are commonly used in equipment. For example, this type of switch can be found in a home computer and a large piece of manufacturing equipment.
The main reason for choosing the DPST design is the safety consideration in worldwide markets, because many global wiring systems are generally non-electrically polarized. By using the double-pole, single-throw switch, the contacts can cut off power to both the line and neutral when flipped into the off position.
Switch markings are symbols printed on switches to indicate their function, type, size, voltage, and current ratings. Switch markings include letters that indicate the switch's status, such as “on” or “off,” as well as letters that identify the switch type, such as “D” for double pole and “C” for single pole.
Answer. NO terminal, NC terminal and COM terminal represent contact terminals' symbols. Each symbol means a single terminal itself: Normally Open terminal, Normally Closed terminal and Common terminal respectively. On the other hand, contact point a, contact point b and contact point c represent contact structures.
A safety switch quickly turns off the electricity supply if an electrical fault is detected. They are considered a back-up and don't prevent all electric shocks.
Safety Sign – A lightning bolt or bolt through a hand. Indication – Presence of High Voltage electric equipment nearby. Bolt-through-Hand. Safety Sign – Lightning bolt on the bottom of the shoe. Indication- Danger of explosion from static electricity.
SP: Single Pole, one circuit controlled by the switch.DP: Double Pole two independent circuits controlled by the switch which are mechanically linked. Note: “Pole” should not be confused with “Terminal”. The DPST switch, for example has four terminals however is a Double Pole (DP) and not a four pole (4P) switch.
AC switches are designed to handle alternating current (AC), which is the most common form of electricity supplied to homes and businesses. Alternating current periodically changes direction, oscillating between positive and negative polarities.
N/O indicates a Normally Open ( N.O.)contact that is single throw . N/C indicates a Normally Closed ( N.C.) contact that is single throw . C/O indicates a Changeover contact ( often noted as a Form C contact ) that is double throw to open and closed positions .
A one way light switch has two terminals which is a common marked as COM or C. The common is for the live wire that supplies the input voltage to the switch. The other terminal is marked as L1 and is the output to the light fixture.
Coded magnetic switches — also known as non-contact coded magnetic safety switches – incorporate pole-sensitive magnetic sensors with coded magnetic actuators to create defeat resistant switches that are only triggered with the correct magnetic code or pattern.
Your safety switches can be quickly identified by looking for one or more buttons marked 'T' or 'test' at your switchboard. You will need to look carefully as there may be more than one and they can be different colours, shapes or sizes.
A common style of a switch is a rocker design, which includes on/off markings. To meet the standard IEC 60417, the symbol for ON is “I” (a straight line) and the symbol for OFF is “O” (a circle).
The I and 0 are based on the binary system, with “I” as the number one and “0” as zero. Pushing the side of the button with “I” will turn your device on. Conversely,”0” means off. An easy way to differentiate is to think of the 0 as allowing your electronics to do zero functions, therefore, turned off.
A one way light switch has two terminals which is a common marked as COM or C. The common is for the live wire that supplies the input voltage to the switch. The other terminal is marked as L1 and is the output to the light fixture.
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