Connector Keying
Keying is the notch, wedge or asymmetric housing arrangement that lets a socket mate only with its correct counterpart. It physically prevents two different connectors with the same pin count from being mixed up. Colour coding serves the same purpose but is no substitute for physical keying.
It is ordinary for a machine to carry several sockets of the same type and the same pin count: motor, valve block, sensor group and remote control receiver. If these sockets can be plugged into each other, sooner or later one will be mated wrongly during installation or service, and the result can be reverse polarity, a short circuit or a command sent to the wrong output.
- Mechanical keying: the notch or wedge on the housing only enters the matching counter housing.
- Colour coding: differently coloured housings within the same family allow quick identification.
- Labelling: putting a permanent label on both sides is the third layer supporting the keying.
Choosing different keying for different functions at the design stage prevents hours of fault-finding in the field before it starts. If an existing system has no keying, at least mark the sockets with different coloured sleeving and permanent labels; during commissioning, also verify each socket by measuring the expected voltage before plugging it in.
Context in which this term is used: Installation, redundancy and field continuity