1     Scope
 2     References
 3     Definitions
 4     Electrical characteristics
        4.1     Generator characteristics
                  4.1.1     Open circuit measurement
                  4.1.2     Test termination measurements
                  4.1.3     Short-circuit measurement
                  4.1.4     Output signal waveform
        4.2     Load characteristics
                  4.2.1     Input current-voltage measurements
                  4.2.2     Input sensitivity measurements
                  4.2.3     Cable termination
                  4.2.4     Fail-safe operation
        4.3     Interconnecting cable electrical characteristics
 5     Circuit protection
Appendix I  –  Guidelines for application
        I.1     Example on an interconnecting cable
                  I.1.1     Length       
                  I.1.2     Cable physical characteristics
                  I.1.3     Cable termination
        I.2     Examples of generators and receivers
                  I.2.1     ECL – Emitter coupled logic technology
                  I.2.2     Fail-safe biasing of receivers