ISA 50.00.01 : 1975

1 Scope and purpose
2 Definitions
3 Standard signals
  3.1 Polarity
  3.2 Transmitters
  3.3 Receivers
4 Standard transmitters
  4.1 General
  4.2 System compatibility
  4.3 Classification
  4.4 Load resistance specification
  4.5 Electrical isolation
  4.6 Ripple and noise content
5 Standard receivers
  5.1 Inputs
  5.2 Outputs
  5.3 Isolation
6 System
  6.1 Signal common
  6.2 Power supplies
  6.3 Transmitters
  6.4 Receivers or signal processors
  6.5 Test power sources
Annex A - Supportive information

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