Glossary · System coordination, integration and orchestration
Permission signal
Also known as: Release signal, Enable signal
German: Freigabesignal
In industrial automation, a permission signal is a signal by which one machine, controller or operator allows another to perform an action, such as entering a shared area, taking over a part or starting a sequence; without it, the action must not start.
- System integration
In one sentence
A permission signal allows another machine or controller to perform an action, such as entering a shared area or starting a sequence.
Example
The conveyor controller sets the permission signal for the robot only when the pallet is clamped and the conveyor segment is stopped.
How it applies
- Engineering: Define precisely what the permission covers, when it is granted and when it is withdrawn. A permission should be withdrawn automatically when its preconditions no longer hold, not only at the end of the sequence.
- Commissioning: Test what happens if the permission drops while the permitted action is running; the receiving machine needs a defined reaction.
- Safety: A permission signal from standard control logic coordinates machines. Where it protects people, the function must be implemented as a safety function with the required integrity; see Interlock.
- Documentation: List permission signals with their meaning and conditions in the interface specification, and use the same signal names in diagnostics and service documentation.
Permission signal vs. ready signal
A Ready signal reports a state: "I am able to do something." A permission signal grants a right: "You may do something now." A handshake often combines both, together with a Request signal.