Abstract: An external battery pack held in sealing engagement with electronics equipment by a safety latching assembly including a guide frame having a strike plate slideably engaged therein with the strike plate held in an operative position by a shear pin constructed to shear when internal gases in the battery reach a sufficient pressure. Shearing the pin allows the strike plate to move to an open position wherein the battery is vented to the atmosphere.

Abstract: The purpose of the disclosed structure is to extract features from the emissions of quasi-periodic signal sources, such as piston engine powered vehicles and the like, after which pattern classification can proceed by any of a number of known methods. The structure consists of a phase locked loop, a bank of discrete-time filters, and a microcomputer. The filter bank is tuned by changing the clock rates, which are derived from the phase locked loop, which is locked to the signal fundamental frequency. The microcomputer is used to acquire the fundamental frequency and the filter tuning is such that each filter tracks a single harmonic.