The rapid development of new technologies in telecommunications, electric power transmission and distribution, and electric railway systems has made the earlier issue of the Directives (1960 edition) out-of-date and this former issue is therefore being replaced completely.

The present Directives supersede the 1963 edition approved by the 2nd Plenary Assembly of CCITT in New Delhi 1960. The 1963 Directives were amended in 1965, 1974, 1978 and 1982. They provided a comprehensive description of electromagnetic effects due to the close proximity of telecommunication lines to power and electrified railway systems, containing regularly updated findings in this field and reflecting the current state of the art.

The power network is an important environmental factor affecting telecommunications facilities. Steady state induction at fundamental and harmonic frequencies often causes signal interference (noise) in telecommunication systems.

Excessive voltages and currents on telecommunication lines as a result of coupling from nearby electric power and electrified railway lines might present a danger to the trained staff working on the lines, to the equipment and facilities of the telecommunication system and to the users of telecommunication terminal equipment.

In most cases voltages and currents continuously induced longitudinally into the telecommunication line do not usually result in dangerous conditions. However, they may result in disturbances which can seriously affect the performance of telecommunication systems.