Should a key switch activate the operator’s open input, single-button input, hold-open input, or three-button control terminals?

A key switch should connect to the operator input that matches the intended command. Use OPEN for open-only access, SINGLE BUTTON or CYCLE for repeated open-stop-close sequencing, a documented HOLD OPEN input for maintained operation, and three-button terminals only when separate open, close, and stop commands are required. Never select the terminal by label alone.

Choose the Input by the Required Gate Behavior

The key switch does not determine the operator’s movement sequence by itself. It changes the state of a control-board input, and the board decides whether that input opens, cycles, closes, stops, pauses the automatic-close timer, or remains active as a hold-open command.

The same momentary normally open contact can produce different results on different terminals. It may open only, advance through an open-stop-close sequence, or command a dedicated direction. Board programming and automatic-close settings can also change what happens when the gate is already open.

Use the OPEN Input for Routine Open-Only Access

An OPEN, FULL OPEN, ACCESS CONTROL, RADIO OPEN, or similar terminal is commonly appropriate when the key should authorize entry and the operator will close through its normal timer or another control. A momentary key turn typically opens a closed gate and may reverse a closing gate.

Do not assume every OPEN input behaves identically. On some boards, another activation while the gate is open resets or holds the timer-to-close. On others, especially when automatic close is disabled, the same input may close the open gate or require a separate close command. Confirm the terminal description for the exact board revision.

Open-only wiring is usually the cleanest choice for residents, employees, or controlled entry when the key switch should not manually command closing.

Use SINGLE BUTTON, SBC, CYCLE, or STEP for Sequential Control

A single-button input is intended for one contact to advance the operator through a programmed sequence. A common sequence is OPEN, STOP, CLOSE, STOP, although the exact order and response at the limits vary by control board.

This input may be appropriate when the same key switch must open an idle gate and later close or stop it with another key turn. It is usually paired with a momentary contact so the input releases after each command. A maintained switch can leave the circuit continuously active and prevent the board from seeing the next distinct activation.

The next command depends on the gate’s current position and movement state. An open-only input is often easier to understand when automatic closing is already configured.

Use HOLD OPEN Only for an Intentional Maintained Mode

A maintained key switch should connect to a dedicated HOLD OPEN input or to an OPEN or EXIT input that the operator manual specifically identifies as compatible with continuous activation. While the contact remains active, the board may hold the gate at the open limit and pause the timer-to-close.

Verify the release behavior before using this arrangement. Returning the key to OFF may start a fresh timer countdown, restore normal automatic closing, or leave the gate open until a separate close command is received. An active vehicle loop, photo eye, sensing edge, stop circuit, or fault can also prevent closing after the hold-open contact releases.

Do not use FIRE, emergency-open, shadow-loop, or safety terminals as convenience hold-open inputs unless the operator documentation specifically assigns that function. Those inputs may have different priority, alarm, reset, or safety behavior.

Use Three-Button Terminals for Separate Directional Control

Three-button control terminals are appropriate when the station must provide independent OPEN, CLOSE, and STOP commands.

A simple two-wire key switch cannot provide all three functions. The station may need separate contact blocks, additional conductors, and a normally closed stop circuit. A three-position OPEN-OFF-CLOSE key selector usually provides open and close contacts, but its center position normally releases both contacts; it does not automatically activate a dedicated STOP terminal.

Stop logic deserves special attention. Some operators require a normally closed stop loop that must remain continuous for normal operation. Others use a different control-station arrangement. Match the station diagram, conductor count, and board settings rather than assuming all three-button controls are interchangeable.

Garage Door Operators May Require an Interface

A residential garage opener may use a proprietary digital wall-control circuit instead of standard dry-contact terminals. In that case, none of the labels above should be assumed available at the wall-console connection. A model-specific dry-contact adapter, supported receiver, or approved interface may be required.

Commercial garage and industrial door operators are more likely to provide single-button or separate open-close-stop control inputs, but the switch action and stop logic must still match the operator documentation.

Technician’s Corner

Field Note: Watch the Input LEDs Before Moving Wires

Operate the key switch and confirm which board LED changes state. If the expected OPEN, SBC, CLOSE, or STOP indicator does not respond, inspect the contact type, common terminal, wiring, relay, and input programming before selecting another terminal.

Field Note: Maintained Inputs Can Dominate Other Controls

A continuously active OPEN or HOLD input may pause the timer and prevent another keypad, receiver, loop, or key switch from creating a new transition. The gate can appear unresponsive even though the other devices are operating their relays correctly.

Field Note: Directional Close Commands Need Clear Visibility

A key station that directly commands CLOSE should be positioned according to the operator instructions so the user can observe the moving gate and remain outside the gate’s path.

Field Note: South Florida Moisture Can Change the Input State

Condensation, salt air, wind-driven rain, and water entering conduit can corrode contacts or bridge terminals. A momentary input may appear maintained, while a normally closed stop loop may open intermittently. Inspect the enclosure, conduit seals, splices, and terminal block.

Before You Select the Terminal

• Define whether the key should open only, cycle, hold open, close directly, or provide open-close-stop control.
• Record the operator model, control-board part number, revision, and current programming.
• Confirm the terminal’s behavior when the gate is closed, opening, open, closing, and stopped.
• Verify momentary or maintained action and N.O., N.C., SPDT, or multi-pole contacts.
• Check timer-to-close behavior and what happens when a maintained contact releases.
• Confirm conductor count, common-terminal requirements, adapter needs, and key-removal positions.
• Keep emergency, fire, loop, stop, and monitored safety circuits on their documented terminals.

Final Input-Selection Rule

Use OPEN for routine open-only access, SINGLE BUTTON or CYCLE when one momentary switch must advance a sequence, HOLD OPEN only for a documented maintained mode, and three-button terminals when separate open, close, and stop control is required. Before selecting hardware, verify the operator model, board generation, terminal logic, voltage, connector type, switch action, timer programming, and safety-device requirements.

Related Technical Categories

• Key Switches and Key Stations
• Gate Operator Control Boards
• Open-Close-Stop Control Stations
• Access-Control Relays and Interfaces
• Garage Door Dry-Contact Adapters
• Photo Eyes, Sensing Edges, and Vehicle Detection