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