Abstract: A 14.4 kilobit/second modem uses an encoding scheme in which groups of five bits are encoded as one of thirty-two (2.sup.5) possible code groups. This is done by using quadrature amplitude modulation and a 6 by 6 space-state constellation which allows a maximum of thirty-six different points to be encoded. Since only thirty-two points are needed the four outer corner points of the constellation are not used. In order to achieve the desired 14.4 KBPS data rate the baud clock must run at 2880 Hz. However, this bandwidth is very close to the maximum bandwidth available on voice-grade telephone lines. Accordingly, data encoding and data recovery techniques must be used which maximize the probabilities of correctly receiving the encoded data signals.

Abstract: An automatic transversal equalizer is provided wherein the input signal is sampled and stored on a series of capacitors. The capacitor voltages are sequentially recalled for application to an analog multiplier which also receives a sequence of coefficient voltages which have been stored by a second series of capacitors. The single analog multiplier performs the functions of the plural voltage controlled attenuators of prior art equalizers.