The present document is one of the parts of the specification of the Digital Enhanced Cordless Telecommunications (DECT) Common Interface (CI). This part of the DECT CI specifies the speech and audio coding and transmission requirements. In order to ensure satisfactory interworking of different portable and fixed units, it is necessary to specify the transmission performance of the analog information over the digital link. This requires not only use of a common speech algorithm, but also standardization of frequency responses, reference speech levels (or loudness) at the air interface and various other parameters. The present document applies to DECT equipment which includes all the necessary functions to provide real-time two-way speech conversation and stereo audio transmission. Several speech services are defined in the present document, including conventional 3,1 kHz telephony, wideband 7 kHz voice transmission, super-wideband 14 kHz and fullband 20 kHz service. DECT Fixed part providing such services may be connected to the public circuit switched (PSTN/ISDN) network, to private networks or to the Voice over Internet Protocol (VoIP) network.