Abstract: A mechanism for indicating the degree of alignment of a photoelectric sensing system produces a pulse width modulated signal in response to the intensity of light received by the sensing system. That signal has pulses which occur at a fixed frequency, but which vary in duration in response to the received light intensity. The pulse width modulated signal drives an indicator, such as a sound or light emitter. With this technique, the output of the indicator is pulse width modulated to indicate the intensity of the received light and thus the degree of alignment of the sensing system.