An error detection system for a discrete receiver. Sequences of bits together forming frames of information comprise the signal received by the discrete receiver. The signal is decoded by a convolutional decoder and is re-encoded by an encoder. Successive portions of nonoverlapping sets of adjacently positioned bits of the re-encoded signal formed by the encoder are compared with corresponding bits of a signal representative of the signal received by the receiver. When excessive numbers of the successive portions of the signals which are compared include bit dissimilarities, a bad frame indication is generated.