Output signal switching device

In the context of automation and more specifically machinery safety, Output Signal Switching Device (or OSSD) refers to the interface of a sensor designed for reliably signalling a safety-related event, usually the crossing of an immaterial barrier.

Instead of a continuous passive signal, the technology relies on 2 independent channels carrying the same information output by the OSSD device.

• Idle signal is 24 V, periodically shortly pulsed to 0 V (pulses are not synchronous) in order for the receiver to ensure there is no shortcut to either 0 V or 24 V.
• Active signal is when both lines present 0 V; however a single line presenting 0 V for a duration longer than the test pulses is sufficient to signal the event.