Industrial Engineer · phase 3 of 16 · noun
Interlock
Logic that prevents an operation when a condition would make it unsafe or damaging.
The Explain card
- Plain English
- An interlock is logic that blocks an action while some condition would make it dangerous or damaging. It sits in series with the command and wins every time.
- Example
- The press cannot cycle while the light curtain is broken. The curtain's clear bit is a contact on the cycle rung, and no operator input gets around it.
- Why it matters
- Interlocks are how the program encodes what the machine must never do. They belong in one obvious place per output, so a technician can find every reason a motor will refuse to run without reading the whole project.
- Hook
- The reasons the machine says no.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
The safety PLC permits the conveyor to start only after the guard-door interlock reports that the gate is closed and latched.
How it is built
- inter- prefix between or mutually
- lock base to fasten or secure
Where it came from
- Origin
- an English formation from the Latin-derived prefix inter- and the English word lock
- Entered the language
- 1840s
- What changed
- The earlier verb described things locked together, and the noun later named mechanisms and control arrangements that coordinate equipment states.
How it is spelled
- Pattern
- The prefix inter- joins directly to the base without a hyphen.
- Pattern
- The base keeps the ck spelling used after its short o sound.
Spelled like
- interlock
- interlink
- padlock
- deadlock
Broken into chunks
-
inter-
- interface
- interconnect
-
lock
- lockout
- padlock
What it sits beside
Same subject
- permissive
- guard switch
- safety relay
- emergency stop
Same shape
- interlink
- interconnect
- interchange
machine-safety signals
- guard interlock
- emergency-stop input
- light-curtain input
control conditions
- interlock
- permissive
- inhibit
Where it sits in the deck
Phase 3: PLC Program Organization and Execution
How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.
