Fool proofing chain broken

What does "fool proofing chain broken" mean?

I've never heard the term????

Is that written in a manual?

It is one of connector discrepancies which can be detected by GVI.please go to page 84 of file I have just sent

Still need a reference. I dug into the Standard Wiring Practices Manual..... no mention of the phrase.

Page 84.....
  
     
  
The only time I've seen a chain is in reference to a programming pin adapter plug that must stay with the aircraft when a component is changed.

Two examples are the engine FADEC units and the newer Standby (Attitude, Heading, Altimeter, Airspeed) Indicators in the cockpit.

Engine specific strapping (or coding) is on one plug that attaches to the FADEC. It is chained to the engine.

Aircraft specific data is coded to a plug that connects to the Standby Indicator. A chain connects it to the aircraft wiring harness and not the instrument.

Here's a picture of a FADEC unit. I'll have to take a pic of one (with the programming plug) on an actual engine.
  
     
 

Patent No.US20100167567
is a connector with foolproof structure that is protruded inside the receiving hole for blocking an insertion of an incompatible plug

So engine characteristics plug is chained to engine to prevent connecting wrong plug by fools so the chain is foolproofing structure, correct me if I'm wrong.

I'm just giving you my best guess on this question.

Plugs use alignment keys to keep it in the correct position before tightening down. There is no chain.

The alignment keys make sure that the wrong plug is not installed on a specific receptacle..

The keys are different on each plug if a large number of plugs are in one area.
  
     


The only chains I've seen are used on the programming plug mentioned above.