Abstract: A digital speech coding circuit makes use of linear predictive coding, vector quantization and difference, Huffman coding, and excitation estimation to produce digital representations of human speech having bit rates low enough to be transmitted over such channels as telephone lines and at the same time being capable of being synthesized in the receiver portion of the circuit to produce analog speech of high intelligibility and quality. The transmitter portion of the circuit comprises a series connection of a low pass filter, analog to digital converter, linear predictive coding module comprising five resonators for establishing five center frequencies and bandwidths of the analog speech, vector quantization module comprising binary representation of the likely combinations of resonances found in human speech, Huffman coding module, a variable bit rate to fixed bit rate converter, and optionally, an encryption module.