This Standard recommends a simple system of insulation coordination for nominal 240/415 V, 50 Hz electrical installations in multiple earthed neutral (MEN) systems to avoid damage to wiring and equipment due to transient voltages exceeding 2500 V caused by lightning discharges and switching. Circuits in some installations may be protected for lower overvoltages, but this is not dealt with in this Standard. (For guidance see AS 1768.) This Standard does not apply to the protection of installations from temporary overvoltages which could result from faults in the electricity supply system. It does not apply to the protection of equipment connected to both electricity supply and information technology services (e.g. telephone cables and TV antennas). Consideration needs to be given to a common earthing system for the protection of all electrical services.NOTE: Reference should be made to AUSTEL mandatory Technical Standard 001 which specifies requirements for overvoltage protective devices in equipment to be connected to telecommunication networks. For most applications of this Standard, the telecommunication networks need not be taken into consideration. However, if connections are to be made between systems, or if both systems are enclosed in common ducts, the requirements of this Standard and AUSTEL mandatory Technical Standard 001 should be met. Reference should also be made to AS 3260.