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TIA/EIA standard IS-641 is a speech coding standard released in 1996 and used in some computer and telecommunications networks in the United States. The main usage was in the U.S. TDMA networks defined by IS-136. The bit rate of the speech codec is 7.4 kbit/s. This codec is the same as the 7.4 kbit/s mode in the AMR speech codec.[citation needed] The standard was superseded[citation needed] by TIA/EIA-136-410's release in 1999.
This document gives a description of the Nokia/JSH speech and channel codec for the TIA IS-641 Enhanced Full Rate Codec. The codec consists of a 7.4 kbit/s ACELP speech codec and a 5.6 kbit/s channel codec (Forward Error Correction).