electronic seismic instrumentation, namely compasses, depth sensors, acoustic positioners; streamer cable position control devices, depth control devices; acoustic ranging systems, namely shipboard support digital signal processing equipment for sensing heading and controlling depth; streamer assemblies for towing by boat; heading sensors; roll sensors; acoustic release mechanisms; transmitters, receivers and transponders and buoys; computer program software for use in seismic surveying; and communication equipment, namely receivers and transmitters