Industrial Engineer · phase 1 of 16 · noun

Terminal Block

Removable or fixed connector where field wiring lands on an I/O module or base.

The Explain card

Plain English
The terminal block is the strip of screw or spring clamps where the field wires physically land. On many cards it unplugs from the module so you can swap the card without lifting a single wire.
Example
A technician replaces a failed input card by pulling the terminal block off the front, seating it on a new card, and never touching the wiring.
Why it matters
Loose terminals cause more intermittent faults than any bug in the program. A removable block also means the block can be seated one slot over, which puts sixteen wires on the wrong card.
Hook
Most ghosts in the machine live under a screw.

Word knowledge

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

To replace the failed discrete input card, unplug the terminal block from the module face and seat it on the spare without lifting the field wires.

Why these words
  • terminal Latin terminalis, of a boundary, from terminus, end supplies the end-point half, so the phrase is about where a conductor stops
  • block Old French bloc, log, from a Germanic source akin to Middle Dutch blok, tree trunk names the solid body that groups those end-points into one piece a hand can pull
Where it came from
Origin
English electrical compound from Latin terminalis, of a boundary, from terminus, end, and Old French bloc, log, from a Germanic source akin to Middle Dutch blok
Entered the language
1920s
What changed
Terminal moved from of a boundary, to the end of a line, then to the stud a conductor stops at. Block moved from a log, to a solid lump, then to a grouped unit. Electrical catalogs of the 1920s joined the two, and PLC drawings still print the pair across the front of the card.
How it is spelled
Pattern
Latin -alis yields English -al, so terminal sits with final and original
Pattern
After a short vowel, English writes /k/ as ck, so block sits with rock and stock
Breaks the pattern
the noun phrase stays two words; a hyphen appears only when the pair modifies another noun
Breaks the pattern
English never writes terminalblock; German catalogs concatenate

Spelled like

  • final
  • original
  • rock
  • stock
Broken into chunks
  • termin
    • terminate
    • terminus
    • exterminate
  • al
    • final
    • original
    • criminal
  • block
    • blockade
    • blockage
    • unblock
What it sits beside

Same subject

Same shape

  • terminal strip
  • terminal board
  • fuse block
  • junction block

I/O family

Open terminal compounds

  • terminal strip
  • terminal board
  • terminal screw

Block compounds

  • fuse block
  • junction block
  • distribution block

Where it sits in the deck

Phase 1: PLC Controller Hardware

The box itself, from processor and rack to the modules that plug into it, because nothing else in the deck lands until you know what a PLC physically is.

Neighbours in this phase