An automatic noise threshold circuit and method automatically sets an operating threshold for a signal receiving section of a laser pulse transmitting device such that a constant noise pulse firing rate is output from a detector to provide maximum return signal sensitivity and enable detection of the weakest possible laser pulse in order to obtain maximum performance out of a laser range finder. The circuit sets the noise pulse rate at that point at which, in conjunction with a firmware based process, the actual return signals from the target can be discrimintated from the accompanying noise.