Remote Control Modes - Local vs Remote

This amounts to a short note really.  

Nothing too mind bending, just the usual confusion with language we sometimes have....

Often Control Selectors and Mode switches are provided to assist off-normal operation or maintenance.

These days most control is done remotely, with Local control being the abnormal case.

Local control refers to the control you do when you are remotely located ? Doesn't make a lot of sense linguistically at least. 

So LOCAL really means LOCAL to the controlled Equipment.  REMOTE means controlled remotely from the MCR/PCR/MCC etc. normally a remote central location.

Of course we have confused the issue somewhat with the choice of language in SCADA where Supervisory control is managed from the REMOTE control location, and the Remote Terminal Units [RTU] are provided in the locality of the equipment.

So what of a Remote/Local control switch ?

A Remote/Local control selector switch can often be situated in proximity to the controlled plant [i.e. LOCAL to the equipment] and allow an operator to take control locally and avoid the need to interact or accept remote supervisory commands.

Switching the Selector to REMOTE allows the equipment to be controlled REMOTELY from a SCADA Master Station.

The important point to remember is that LOCAL always refers to the locality of the actual equipment.

If you have a particularly fine example of local control remote/local selector switch that you would like to contribute a photo of, please feel free to make a comment or send an email.

Happy Christmas.

Chris Smith

Sydney, Australia