pushtobreak

Push-to-break, often abbreviated PTB, refers to a type of electrical pushbutton switch in which pressing the actuator opens an electrical circuit that is normally closed at rest. The term is used in control and automation contexts to describe the action of interrupting current flow by way of a mechanical push.

Operation and configurations

PTB devices are typically designed to break the circuit when actuated. In its most common form, the switch is normally closed and becomes open while the button is pressed, returning to the closed state when released (momentary). There are also maintained (latching) variants where the actuation toggles the circuit state until a subsequent action occurs. PTB switches can be used alone (SPST) or combined in multi-pole assemblies (e.g., DPST/DPDT), providing multiple contacts that break together.

Construction and characteristics

PTB switches may be momentary or latching, with a range of actuator shapes to suit panels, keyboards, or safety enclosures. They are selected based on electrical ratings (voltage, current), mechanical life, tactile feedback, and enclosure protection. Commonly integrated into control panels, machine safety interlocks, and emergency-stop-related circuits, PTB devices are designed to ensure a deliberate actuation is needed to interrupt power or a process.

Applications and standards

Push-to-break controls appear in industrial automation, safety circuits, process control, and door interlocks. They are specified in standards for control devices and pushbuttons, often referenced alongside push-to-make counterparts. Durability and contact configurations vary by manufacturer and application requirements.

See also: pushbutton switch, normally closed contact, push-to-make.