typical arrangement for decoding convolutional codes wherein at time t t o the four most likely paths representing the path leading into each of the four states and their associated metrics are known and stored in most likelihood storage means 24 two channel samples are received during the time interval t o t o t and these two samples are correlated with the assumed prior channel digits in accordance with equation 1 and added to the existing metrics to form eight new metrics two for each state in the portion of fig3 corresponding to the state diagram of fig2 the two metrics for each state are compared in comparators 26 and the largest of the two competing metrics is determined for each state and the path corresponding to the larger metric along with the metric itself is stored in most likelihood storage means 24 for future calculations it can be shown that with high probability all four surviving paths at each node in time have previously emerged from a common state 4 or 5 constraint lengths into the past thus the common path can be decoded as the most likely source subsequence a first arrangement in accordance with the present invention for implementing the viterbi algorithm using analog processing techniques is shown in fig4 a and 5b in fig4 the analog input signal to decoder 22 of fig1 is received at input terminal 30 the.