Abstract: A decoder for forward-error-correcting (FEC) convolutional codes. The decoder uses the Viterbi algorithm for decoding the rate 1/2, constraint length 7 code with generator polynomials x.sup.6 +x.sup.5 +x.sup.3 +x.sup.2 +1, and x.sup.6 +x.sup.3 +x.sup.2 +x+1. The architecture of the instant decoder is appropriate for implementation on a single, monolithic VLSI integrated circuit chip and includes a branch metric calculator circuit which produces output signals representative of input symbol signals. These output signals are supplied to a metric update circuit which evaluates the signals from the calculator circuit and provides decisions to a path update circuit which converges the signals thereto and the output signals of which are evaluated by a majority vote circuit which produces data output signals representative of data input signals.

Abstract: A chemical sensitive field-effect transistor transducer capable of selectively detecting and measuring chemical properties of substances to which the transducer is exposed. The transducer includes a semiconductor substrate material having a certain doping polarity, a pair of spaced apart diffusion regions located at the surface of the substrate material and having a doping polarity opposite that of the substrate material, electrical insulator material overlying the diffusion regions and the surface of the substrate material lying between the diffusion regions, and a chemical selective system overlying the insulator material. The chemical selective system is adapted to interact with certain substances and thereby modulate an electric field produced in the substrate material between the diffusion regions. This modulation is dependent upon the chemical properties of the substances and provides a measure of those chemical properties.