Applicable to equipment designed and intended to be connected directly to a Telecommunication Network, regardless of the source of power. This basic safety publication is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51. It is not intended for use by manufacturers or certification bodies. This standard has the status of a basic safety publication in accordance with IEC Guide 104 and ISO/IEC guide 51. This standard cancels and replaces IEC Guide 105 published in 1985. The contents of the corrigenda of March 2001 and June 2001 have been included in this copy.