2026-09-11 Two toggle switches can look almost identical from the front of a control panel and do completely different jobs behind it. One simply opens a circuit. Another selects between two connections. A third changes two separate circuits together.
The main toggle switch types are SPST, SPDT and DPDT. SPST opens or closes one circuit, SPDT connects one common terminal to either of two contacts, and DPDT operates two changeover circuits with one actuator. These letters describe the contact arrangement. They do not, by themselves, tell you whether the switch has a center-off position or springs back when released.
If you are replacing a switch or preparing an OEM parts order, that distinction is the best place to start. Match the electrical function first, then check the ratings and dimensions.
What do poles and throws mean?
A pole is an independently switched circuit. A single-pole switch controls one circuit; a double-pole switch controls two electrically separate circuits through the same mechanical actuator.
A throw describes the number of selectable contact paths for each pole. Single throw provides one path that can be connected or disconnected. Double throw lets a common terminal connect to one of two contacts.
Think of it as two questions: how many circuits must move together, and how many connections must each circuit choose between?
| Type | Contact arrangement | Typical contact terminals* | Example purpose |
|---|---|---|---|
| SPST | One circuit, one switched path | 2 | Enable or disable one circuit |
| SPDT | One common, two selectable contacts | 3 | Select between two control paths |
| DPDT | Two changeover circuits operated together | 6 | Change two signal paths together |
*Counts refer to simple, non-illuminated contact arrangements. Illumination, duplicated terminals or other features can change the total number of connections. Identify terminals from the manufacturer’s drawing rather than appearance alone.
When a simple SPST switch is enough
An SPST toggle switch suits a job with one basic decision: connected or disconnected. A low-voltage enable circuit is an example, provided the switch is specified for the actual electrical conditions.
There is no second contact path to select. If the operator needs to choose between two modes, an SPDT arrangement may be more appropriate.
“SPST” also does not mean “power switch.” Some small toggle switches are intended for low-level signals, while others carry higher loads. The contact rating determines suitability, not the size of the lever.
SPDT adds a choice, but not necessarily an OFF position
An SPDT toggle switch has a common contact and two selectable contacts. In an ON-ON version, the common connects to one contact in one position and the other contact in the opposite position. There is no maintained center-off position.
An ON-OFF-ON version adds a center position that disconnects the common from both contacts. This can be useful when a control needs two selections and a neutral state.
That is why “three-pin toggle switch” is an incomplete purchasing description. Two three-terminal switches may have different operating functions even though their terminal counts match.
The C&K T Series toggle switch datasheet illustrates this distinction with separate ON-NONE-ON, ON-OFF-ON and momentary options. In that style of function table, NONE means there is no center position; it does not mean center OFF.
DPDT changes two circuits together
A DPDT toggle switch is functionally like two SPDT contact sets linked to one lever. Each pole has its own common and two selectable contacts, allowing two circuits to change with one operator action.
For example, a design may need to select two related signal paths together. DPDT provides the contact arrangement for that task, while the circuit designer determines the connections and required ratings.
DPDT is not automatically a drop-in upgrade for SPDT. The extra contacts may require a different footprint, more space or a different terminal layout. Nor should the two poles simply be paralleled to claim double the current rating unless the manufacturer explicitly permits it.
Momentary and maintained describe what happens when you let go
A maintained toggle stays in its selected position after release. A momentary toggle returns from a spring-loaded position when the operator lets go. A single switch can combine maintained and momentary positions.
Manufacturers often mark a momentary position as MOM. or place parentheses around ON, but the notation should always be checked against the datasheet. Buying by “ON-OFF-ON” alone is risky if the original function requires spring return.
Keep these checks separate: first identify SPST, SPDT or DPDT; then identify the positions; finally confirm which positions, if any, are momentary.
A real example: TMS3T5B2M6RE
TMS3T5B2M6RE is listed in the EASYIEE switch catalog. TE Connectivity identifies it under part number 2267078-6, with a single-pole, double-throw arrangement and an ON-OFF-ON operating function across three positions.
This example shows why a complete ordering code is useful. “SPDT toggle switch” describes the broad contact arrangement; the exact part identifies a specific combination of function and construction.
Use the TE Connectivity product page and linked drawing to check the terminal layout, mounting details and electrical requirements. The example is not a recommendation to replace another switch without checking those details. Availability and lead time should be confirmed when requesting a quote.
The checks that prevent a wrong replacement
After matching the contact function, compare the electrical rating under the actual load conditions. AC and DC ratings are not interchangeable. A switch suitable for a resistive load may need different consideration when switching an inductive load or a circuit with high inrush current.
For low-level control signals, check whether the contact material and any minimum-load requirements suit the circuit. Selecting the highest current rating is not always the right answer for a small signal.
Next, compare the panel cutout, bushing thread, permitted panel thickness, actuator length and rear clearance. For a PCB-mounted switch, verify the footprint, pin spacing and orientation. A part can fit through the panel yet fail to align with the board behind it.
Finally, check environmental requirements. Sealed terminals for assembly cleaning do not automatically establish that the exposed panel installation is waterproof. Use the manufacturer’s stated protection rating and installation conditions.
What to include in a toggle switch RFQ
If an existing assembly specifies a full manufacturer part number, send that code first. Add the required quantity, delivery date and whether alternatives are allowed. For an unidentified replacement, include clear photographs of the markings and terminals, along with the operating function and mounting dimensions.
A useful request could read: “Please quote TMS3T5B2M6RE / TE 2267078-6 for 200 units. Exact part preferred. List any alternatives separately for engineering approval.” Adjust the quantity and requirements to your project.
For a new selection, describe the poles and throws, maintained or momentary action, load voltage and current, termination style and installation requirements. These details help avoid a quotation for a switch that looks right but behaves differently.
If the switch is one line in a larger assembly, our BOM sourcing guide explains how to organize the complete component enquiry.
Send EASYIEE your switch part number or BOM for a quote. Include the quantity and required delivery date so the enquiry can focus on the exact component and current sourcing options.
