This Recommendation contains the specification of an embedded Adaptive Differential Pulse Code Modulation (ADPCM) algorithms with 5-, 4-, 3- and 2-bits per sample (Le.,at rates of 40, 32, 24 and 16 kbit/s). The characteristics below are recommended for the conversion of 64 kbit/s. A-law or p-law PCM channels to/ from variable rate-embedded ADPCM channels. The Recommendation defines the transcoding law when the source signal is a pulse-code modulation signal at a pulse rate of 64 kbit/s developed from voice frequency analog signals as fully specified by Blue Book Volume, Recommendation G.711. Applications where the encoder is aware and the decoder is not aware of the way in which the ADPCM codeword bits have been altered, or when both the encoder and decoder are aware of the ways the codewords are altered, or where neither the encoder nor the decoder are aware of the ways in which the bits have been altered can benefit from other embedded ADPCM algorithms.