1. Private Communication Networks for Electric System Operation.- 2. Communication Problems in Electric System Operation.- 3. Communication Circuits in the Power Network.- 4. Properties of Power Lines in the Carrier Frequency Range.- 5. Characteristics of Power Line Carrier Channels.- 6. Carrier Communication Networks.- 7. Carrier Communication Terminals.- 8. Measuring Methods and Measuring Equipment.- 9. Appendix.- List of Abbreviations.