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Rocker switch specifications often look more complicated than they really are. Terms like (ON)-OFF, ON-OFF, SPDT, and DPDT appear in datasheets, catalogs, and purchase orders. For engineers, DIY designers, and company buyers, this shorthand can feel like a coded language.
This guide breaks down rocker switch functions in plain terms. It explains what the parentheses mean, how single-pole and double-pole switches differ, and how to match switch logic to real applications.
Cracking the Switch “Code” in Datasheets
Most rocker switch confusion starts with the symbols printed in the function description. These symbols describe how the switch behaves mechanically, not how it looks.
Two things matter most:
- Whether the switch returns automatically or stays in position
- How many circuits the switch controls at the same time
Once you separate these ideas, the labels become easier to read.
What Does (ON) Mean in a Rocker Switch?
In switch specifications, parentheses matter.
When you see (ON), it means the switch position is momentary. The switch only stays active while you are pressing it. When you release it, the rocker returns to its default position.
This behavior is also called spring return or self-resetting.
A momentary rocker switch behaves like a doorbell. Press it, the circuit closes. Let go, the circuit opens again.
What Does ON (Without Parentheses) Mean?
When you see ON without parentheses, it means the switch position is latching. The rocker stays in place after you press it.
This is the same behavior as a wall light switch. You press it once and it stays on. Press it again and it turns off.
Latching rocker switches are commonly used for power control, lighting, and system enable functions.
(ON)-OFF vs. ON-OFF: What’s the Difference?
The difference between (ON)-OFF and ON-OFF is entirely about reset behavior.
An (ON)-OFF switch is momentary in the ON direction. You press the rocker, the circuit turns on, and when you release it, the switch returns to OFF.
An ON-OFF switch is latching. Pressing the rocker to ON keeps the circuit on until you manually switch it back to OFF.
This distinction explains why two switches that look identical behave very differently once installed.
Single Pole vs. Double Pole: Understanding SPST, SPDT, and DPDT
The next layer of confusion comes from pole and throw terminology. These terms describe how many circuits the switch controls and how many paths are available.
A simple way to think about this is traffic lanes. Poles are lanes going into the switch. Throws are exits.
SPST: Single Pole, Single Throw
An SPST rocker switch controls one circuit and has one on/off path. This is the simplest type of switch. It opens or closes a single line. SPST switches often have two or three terminals, depending on grounding or indicator options. They are widely used for basic power control. If you only need to turn something on or off, SPST is usually sufficient.
SPDT: Single Pole, Double Throw
An SPDT rocker switch has one input and two possible outputs. It connects the input to one output or the other. This is often described as “one in, two out.” SPDT switches are used when you want to select between two options, such as:
- High / Low speed
- Mode A / Mode B
- Forward signal / Reverse signal
In wiring diagrams, SPDT switches commonly have three or four terminals.
DPDT: Double Pole, Double Throw
A DPDT rocker switch controls two circuits at the same time and switches each between two outputs. This is “two in, two out.”
DPDT wiring is commonly used when you need to reverse polarity. This is why DPDT switches are widely used for DC motor direction control. A familiar example is power window switch wiring. Pressing the switch one way raises the window. Pressing it the other way lowers it. The switch reverses the motor’s polarity internally.
DPDT rocker switches usually have six terminals.
Matching Switch Logic to Real Applications
Understanding the labels is useful, but real clarity comes from matching switch logic to actual use cases.
Power Windows and Linear Actuators
Power windows and electric actuators need the motor to run in two directions. They also need the motor to stop when the user releases the switch. This is why these systems use a (ON)-OFF-(ON) DPDT rocker switch. Each ON position is momentary. The center position is OFF. The switch returns to center when released, stopping the motor automatically.
Automotive Horns
A horn should sound only while the driver presses the switch. This application uses an (ON)-OFF momentary rocker switch, usually SPST or SPDT depending on wiring needs. The momentary action prevents the horn from staying on accidentally.
Headlights and Auxiliary Lighting
Headlights and auxiliary lights are typically turned on and left on. This application uses an ON-OFF latching rocker switch, usually SPST. Once switched on, the circuit stays active until the driver turns it off.
Why Misreading Switch Functions Causes Problems
Many wiring issues come from selecting the wrong switch logic rather than incorrect wiring.
A latching switch used where a momentary action is expected can leave motors running longer than intended. A momentary switch used where a latched state is required can make a system feel broken or unresponsive.
This is why understanding (ON)-OFF meaning and pole/throw structure helps reduce redesigns and returns.
Final Thoughts
Rocker switch labels are compact, but they follow consistent logic. Parentheses indicate momentary action. Poles and throws describe how many circuits are controlled and how they are routed.
Once you understand SPDT rocker switches, DPDT wiring, and the difference between momentary and latching rocker switches, datasheets become easier to read and applications easier to design.
Need a Switch That Matches Your Circuit Logic?
Whether you need momentary, latching, SPDT, DPDT, or complex combinations like (ON)-OFF-(ON), our customized rocker switch solutions support a wide range of electrical and mechanical designs. Contact us to match switch logic to your application requirements.