Selector Switch 2-Position Symbol
Definition: The Selector Switch 2-Position symbol represents a maintained-contact rotary or cam-operated switch that can be turned to one of two discrete positions, used in schematic and wiring diagrams per IEC 60617 and ANSI Y32.2 / IEEE 315 to denote a component that selects between two circuit states — typically On/Off or Manual/Auto — and holds its set position until physically rotated.
Also known as: 2-position rotary switch, selector switch, two-position cam switch, maintained-contact selector, S (2-pos).
What the Selector Switch 2-Position symbol means
The 2-position selector switch symbol identifies a switch whose movable contact can be rotated to sit in one of two stable positions. Unlike a momentary push button, the selector stays in whatever position it is turned to until an operator rotates it again. In schematics it is used to represent operator-controlled mode or circuit-state selection.
In a control-panel wiring diagram the two positions commonly represent ON and OFF, or MAN (manual) and AUT (automatic). The In pin carries the incoming control signal or supply voltage, and the Out pin delivers that signal to the load or control circuit only when the selector is in the active (closed) position.
How to identify the Selector Switch 2-Position symbol
The 2-position selector switch symbol is drawn as a circle (representing the rotary operator) with an arrow or T-bar handle showing the current position, connected to two contact stubs. The arc of rotation indicates two discrete positions. Some representations show the symbol as a rectangular switch block with a rotary indicator and two external terminals labelled In and Out.
Function in a circuit
A 2-position selector switch opens or closes a circuit path depending on which of its two cam positions is engaged. In position 1 the contact between In and Out is closed (or open, depending on the switch wiring), while in position 2 the opposite state is achieved. The switch is a maintained-contact device: it latches mechanically into each position and does not return to a previous state on its own.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-07 defines control-switch symbols. A 2-position selector switch is shown as a make-contact symbol with a rotary operator indicator; IEC 60947-5-1 covers control-circuit selector switches for industrial use. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 represents selector switches as a switch symbol with a rotary operator arc and position markers at each stable stop. The designator is S. |
| Key difference | IEC uses a contact-and-operator drawn per IEC 60617 conventions (small circle for the operator, contact arm inside); ANSI Y32.2 draws a similar but slightly different rotary arc. Functionally and electrically the symbols are equivalent. |
Terminals / pins
| Pin | Name |
|---|---|
| in | In |
| out | Out |
Typical values
Typical contact ratings: 10 A at 600 V AC (NEMA); 4 A–10 A at 230 V–690 V AC (IEC). Number of positions: 2. Rotation angle between positions: commonly 45° or 90°. Cam positions: 2 (Left / Right or 0° / 90°). IP rating: IP54–IP66 (panel mount, sealed front).
Where the Selector Switch 2-Position symbol is used
- Control panels: ON/OFF selector for motor starters, switching the circuit between energised and de-energised states
- Manual/Automatic mode selection for PLC-controlled systems, passing control authority to operator or automation
- Local/Remote selection on VFD and motor-protection relay panels
- Test/Normal selection on protection relay test panels isolating instrument transformer inputs during relay testing
- Power source selection: utility/generator two-position manual changeover applications
- HVAC panels: occupancy or setback mode selection for temperature controllers
Example
In an industrial pump control panel, a 2-position selector switch labelled SA1 is placed with its In pin connected to the 24 V DC control supply and its Out pin feeding the auto-start relay coil. When rotated to MAN the circuit is open and the operator uses push buttons; when rotated to AUT the Out pin is connected, enabling PLC-controlled automatic start.
Key facts
- The selector switch 2-position symbol uses the designator S (for switch) in both IEC 60617 and ANSI Y32.2 / IEEE 315 schematics, typically written as SA (selector, auto) or SS.
- A 2-position selector is a maintained-contact switch: it holds its last-set position mechanically without any continuous operator force, distinguishing it from momentary push buttons.
- The two pins In and Out represent the common feed point and the switched output; when the selector is in the active position the contact between In and Out is closed, allowing current to flow.
- IEC 60947-5-1 governs the electrical and mechanical performance of control-circuit devices including selector switches, specifying endurance of at least 1 000 000 operating cycles.
- Panel-mount 2-position selectors conform to standard panel-cutout sizes: 22 mm diameter (most common) or 30 mm diameter for heavy-duty industrial applications.
- Key-operated 2-position selector switches use a removable key as the operator, providing lock-out capability for safety or access control in electrical panels.
- In NEMA and IEC selector-switch terminology, a 2-position switch has two cam positions and one contact block per phase; a 3-position switch has three positions and requires separate wiring for the centre-off or centre-live condition.
Frequently asked questions
What does the selector switch 2-position symbol look like?
The 2-position selector switch symbol shows a rotary operator (circle with an arrow or T-bar) connected to a single contact pair with two position stops. The In pin represents the incoming supply or signal and the Out pin is the switched output that is connected or disconnected depending on the selector position.
What does the 2-position selector switch symbol mean in a wiring diagram?
It represents a maintained-contact switch with two stable positions that an operator selects by rotating a knob or cam. The switch holds whichever position it is set to and connects or disconnects the circuit path between the In and Out terminals accordingly.
What is the designator for a selector switch?
The standard designator is S (switch), often written SA or SS for selector applications. In IEC 60617 and ANSI Y32.2 / IEEE 315 drawings the reference identifier follows the letter, e.g. S1, SA1.
What is the difference between a 2-position selector and a push button in a schematic?
A 2-position selector is a maintained-contact device that stays in its set position until physically moved; a push button is typically momentary-contact and returns to its default position when released. Both use switch symbols but the selector has a rotary-operator indicator.
What standard defines the 2-position selector switch symbol?
IEC 60617-07 defines graphical symbols for control switches including selector switches. ANSI Y32.2 / IEEE 315 provides the equivalent North American standard. Electrical performance is governed by IEC 60947-5-1 for industrial selectors.
What are typical applications for a 2-position selector switch?
Common applications include On/Off motor control, Manual/Auto mode selection, Local/Remote control transfer, and Normal/Test selection on relay protection panels. In all cases the selector latches into one of two positions and holds that state until an operator changes it.
What is the current rating of a 2-position selector switch?
Panel-mount IEC selector switches are typically rated 4 A to 10 A at 230 V to 690 V AC. NEMA-rated units for the North American market are commonly rated 10 A at 600 V AC. The contact rating must exceed the maximum load current in the switched circuit.
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