INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : G.726

Title :	40, 32, 24, 16 kbit/s Adaptive differential pulse code 
	modulation (ADPCM)

Study Group : XV - Transmission Systems and Equipment

Version : New

Date of adoption : 1990

Notes :	


Recommendation G.726 sets out the characteristics below are recommended 
for the conversion of a 64 kbit/s A-law or µ-law pulse code modulation 
(PCM) channel to and from a 40, 32, 24 or 16 kbit/s channel. The 
conversion is applied to the PCM bit stream using an ADPCM transcoding 
technique. The relationship between the voice frequency signals and the 
PCM encoding/decoding laws is fully specified in Recommendation G.711.

The principal application of 24 and 16 kbit/s channels is for overload 
channels carrying voice in Digital Circuit Multiplication Equipment 
(DCME).

The principal application of 40 kbit/s channels is to carry data modem 
signals in DCME, especially for modems operating at greater than 
4800 kbit/s.

First, Recommendation G.726 provides an outline description of the 
ADPCM transcoding algorithm, it provides further  the principles and 
functional descriptions of the ADPCM encoding and decoding algorithms 
respectively, and finally the precise specification for the algorithm 
computations. Networking aspects and digital test sequences are 
addressed also in Recommendation G.726.



To order the complete text of this Recommendation, please use the 
Order Form for ITU-T Recommendations. An electronic version of this 
form is available on ITUDOC (Winword: UPI=ITU-5265; ASCII: UPI=ITU-2488).