identification codes for electrical protection!

It identifies the characteristics of a protection device, such as a relay or a switch to a switch.
These types of devices protect electrical systems and components from damage when an undesirable event such as a power failure.

A physical device may correspond to a feature number, for example "switch 52 of a.c. power", or a single physical device may have many of the functions associated numbers, for example a numerical protection relay. Letters suffix and prefix can be added to specify further the purpose and function of a device.