The operation of a nonlinear binary detector with hysteresis is investigated. Prior models developed for continuous time inputs are extended for the computationally more efficient discrete-time inputs. The input to the rectangular hysteresis detector is modeled to be a binary signal in the presence of additive independent identically distributed noise. The rectangular hysteresis loop models one of a number of rate independent repeaters in an optical communication link. The link is terminated by a binary discriminator that is tuned to a particular bit duration. The study shows that key calculations to compute the bit error probability can be performed by employing the formalism of discrete Markov chains.