ISA 50.00.01-1975 (R2012)

This document applies to analog dc signals used in process control and monitoring systems to transmit information between subsystems or separated elements of systems.

Its purpose is to provide for compatibility between the several subsystems or separated elements of given systems.

This document need not apply to signals entirely used within a subsystem. When signals are to be transmitted to or received from subsystems or elements provided by different suppliers, they shall comply with the specified requirements for transmitters and receivers herein.