Abstract: A low voltage cutoff circuit, a method of operating the same and a battery backup system incorporating the low voltage cutoff circuit or the method. In one embodiment, the low voltage cutoff circuit includes: (1) a low voltage monitor coupled between an input and an output of the low voltage cutoff circuit, (2) a cutoff switch, coupled between the input and the output and controlled by the low voltage monitor, that closes to couple the input to the output, the cutoff switch subject to failing closed when a voltage of the input is below a threshold and a load couplable to the output contains a short circuit and (3) a short circuit protection circuit, coupled to the low voltage monitor, that senses when the load contains the short circuit and directs the low voltage monitor to prevent the cutoff switch from closing.

Abstract: The direction and rate of rotation of a closed-loop fiber-optic angular rate sensor is determined by employing acousto-optic modulators in each arm of the sensor and determining the frequency difference between the modulators. Since the modulators operate at a relatively high frequency, frequency measurements to within several hertz are implemented by providing the difference frequency and the sign of the difference frequency via the use of electronic mixers. Since the maximum difference frequency is in the order of a few megahertz, standard counters can thus be used to accurately measure the reduced frequency and hence provide information relating to the direction and rate of rotation.