Abstract: A variable depth towed sonar line handling system is arranged to provide a level wind of the sonar cable onto a cable winding drum without significant lateral deflection of the cable. The system includes a boom with sheaves at the inboard and outboard ends and an inboard winch with a cable winding drum. The winch is mounted for axial movement past the boom and is translated axially in synchronism with its rotation so that the fleet angle of the cable remains constant. In preferred embodiments, the winch is located beside the boom and translates fore and aft. This allows the cable to be taken off along the pivot axis of the boom, eliminating cable excursion through the sheaves in boom bobbing. Other features include a fairleading saddle and a combined passive and active shock absorbing system.

Abstract: A portable accelerometer unit is described for measuring deviations or excursions from a datum due to an applied load or force. The portable accelerometer unit includes an accelerometer device mounted by suspension means in a housing, and is operable to generate an output signal in response to the applied load. An electrical circuit is also provided connectible to the accelerometer device to receive the output signal therefrom. This circuit includes at least one operational amplifier stage containing an operational amplifier. This amplifier has two input terminals and an output terminal. One of the input terminals is connected through a first variable resistance to a power supply. The other input terminal is connected to the accelerometer to receive the output signal therefrom. This other input terminal also has a feedback circuit operatively connected to it. The feedback circuit is controlled by a second variable resistance, whereby to effect zeroing of an accelerometer output signal due to gravity.