Switches (toggle/push/slide/rotary/DIP)
Switch
A mechanical device that opens or closes a circuit by hand. Comes in many actions and contact arrangements for selecting, latching and routing signals or power.
Schematic symbol
Switch (SPST)
How switches (toggle/push/slide/rotary/dip) appears in a circuit diagram.
Types & variants
Key specs
Poles & throws
PxTSPST, SPDT, DPDT... how many circuits and positions.
Current rating
AMax current the contacts can switch (often lower for DC).
Voltage rating
VMax voltage across open contacts; AC vs DC differs.
Action
-Momentary vs maintained (latching).
Contact resistance / life
mΩ / cyclesLow resistance, rated mechanical cycles.
Markings
Ratings stamped on the body (e.g. 10A 250VAC). Terminal labels (COM/NO/NC) on many types.
Standard values
SPST/SPDT/DPDT toggles, 8-way DIP, rotary 1P12T etc. Common 3-6A or 10-16A mains rockers.
How to choose
Pick the pole/throw layout for the job, current & voltage rating with margin (derate hard for DC and inductive loads), momentary vs latching, and panel mounting/feel.
Pinout & package
Terminals depend on poles/throws: SPDT has COM, NO, NC. Panel, PCB or chassis mount. DIP switches go in a normal IC footprint.
Example circuits
- Power on/off (SPST)
- Selecting one of two sources (SPDT)
- Reversing polarity (DPDT)
- Setting an address/config (DIP)
Common failures
Contacts wear, pit or oxidise (intermittent), bounce, or weld shut on overload; broken actuator.
How to test
Continuity mode across the relevant terminals in each position - should be ~0Ω closed, open otherwise. Flaky reading = worn contacts.
Substitutes
Same pole/throw and equal/higher current & voltage rating; matching action and mounting.