This part of IEC 61603 describes the characteristics of a digital multiple channel, multiple carrier audio transmission system as an extension to the conference interpretation or similar systems using the frequency ranges 45 kHz to 1 MHz and 2 MHz to 6 MHz. Note: These frequency ranges are also covered by analogue pulse systems used for the same applications. Interference is not expected because both transmission systems are normally not applied at the same time in the same room.