5G communication testing, wireless terminal automated testing
Aerospace communication systems
Precision measurement equipment, radio frequency signal control of radar transmitters
Communication and navigation systems
Optical communication module-related testing
Interconnection of wireless communication base stations
A switch is an electrical component that can interrupt (open) or complete (close) a circuit. Switches come in many forms — toggle, push-button, slide, rotary, limit, reed, DIP, and more — but all share the same core function: controlling the flow of current with a mechanical or electronic action.
In the simplest sense, a switch is a binary device with two states:
Switches are characterized by their poles (independent circuits they control) and throws (positions each pole can connect to). A common "single-pole double-throw" (SPDT) switch routes a signal between two outputs.
In the closed position, the switch contacts touch and current flows from source to load. In the open position, the contacts separate and the circuit is broken.
When the switch is closed, electrons flow through the contacts with very low resistance (milliohms). When open, an air gap blocks current flow, producing a near-infinite resistance. High-quality switches minimize contact resistance, arcing, and mechanical wear to ensure long life.
| Specification | Meaning |
|---|---|
| Poles / Throws | Number of independent circuits and positions |
| Contact Rating | Maximum voltage and current the switch can handle |
| Contact Resistance | Resistance across closed contacts (typ. < 50 mΩ) |
| Insulation Resistance | Resistance across open contacts (typ. > 100 MΩ) |
| Actuation Force | Force required to operate the switch |
| Travel | Distance the actuator moves |
| Mechanical Life | Number of operations before failure |
| Electrical Life | Operations under load before contact wear |
| Termination Style | Through-hole, SMT, solder lug, screw, quick-connect |
Classic bat-style lever for panel mounting. Common in power supplies, instruments, and industrial equipment. Available in SPDT, DPDT, and many other configurations.
Momentary or latching action. Found in keyboards, doorbells, reset buttons, and consumer electronics. Tactile variants give audible or haptic feedback.
Small slider that moves between positions. Common in DIP packages, mode selectors, and hobby electronics.
Spins a shaft to select one of several positions. Used for range selection on multimeters, fan-speed controls, and channel selectors on radios.
Actuated by physical contact with a moving part. Industrial mainstay for detecting end-of-travel on doors, conveyors, and CNC machines.
Two ferromagnetic blades sealed in a glass capsule that close when a magnet approaches. Used in door sensors, bicycle speedometers, and fluid level meters.
Precision switch with a small actuation distance and crisp snap-action. Standard in appliances, safety interlocks, and vending machines.
A row of tiny slide switches in a DIP package. Used to set hardware options on PCBs, such as device addresses or operating modes.
A BJT or MOSFET driven into saturation acts as an electronic switch. No moving parts, fast switching, ideal for microcontrollers driving LEDs or relays.
An electromechanical switch where a coil magnetically closes the contacts. Isolates high-power circuits from low-power control signals.
Uses a TRIAC, MOSFET, or thyristor instead of mechanical contacts. No moving parts, silent operation, long life, but some on-state voltage drop.
An LED and phototransistor pair that switches optically. Provides thousands of volts of galvanic isolation between input and output.
Operated only with a matching key. Used for secure power panels and ignition systems.
Panel-mounted switch with maintained positions (e.g., HAND / OFF / AUTO) for industrial control panels.
Detects objects without physical contact using inductive, capacitive, or magnetic sensing. Common in factory automation.
Actuates when a fluid or gas pressure crosses a threshold. Used in pumps, HVAC, and hydraulic systems.
| Code | Name | Function |
|---|---|---|
| SPST | Single-Pole Single-Throw | Simple ON/OFF switch |
| SPDT | Single-Pole Double-Throw | Routes one input to two outputs |
| DPST | Double-Pole Single-Throw | Switches two circuits simultaneously |
| DPDT | Double-Pole Double-Throw | Switches two circuits between two outputs each |
| 3PST / 4PDT | Triple / Quadruple | Special configurations for complex control |
Always switch the line (hot) conductor, never the neutral. Switching neutral can leave dangerous voltage present on the load even when the switch is OFF.
The single-pole single-throw (SPST) switch is the simplest. It has one input terminal and one output terminal; flipping it opens or closes a single circuit.
Momentary switches return to their default state when released (doorbell). Maintained (latching) switches hold their position until actuated again (light switch).
A pole is an independent circuit that the switch can control. A switch with two poles (DPDT) can switch two separate circuits simultaneously with one actuator.
Generally no. DC creates a sustained arc when contacts open. AC switches are usually derated by 5 – 10× when switching DC. Choose a DC-rated switch for DC loads.
Mechanical life ranges from 1,000 cycles for small tactile switches to 100,000+ for industrial toggle switches. Solid-state switches can last millions of cycles because they have no moving parts.
High-tech Enterprise, Feifeng Talent
Chief Engineer Wang graduated with a master's degree in high-power microwave from the Institute of Electronics, University of Chinese Academy of Sciences.
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