Electronic heading sensors; ultrasonic application measuring and searching machines; digital communication type remote measuring and controlling machines and instruments; computer software (including computer software which is recorded in some recorded media, including CD-ROM's and magnetic discs); depth sensors; acoustic release devices; depth control devices using electronic sensors for use in towing underwater cables; connectors for attaching depth control devices using electronic sensors for use in towing underwater cables to underwater cables; computer software for use in marine seismic surveying and position measuring; measuring apparatus and instruments; electrical communication machines and instruments; electronic machines and instruments and parts thereof; digital readout electronic compasses; 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; parts and fittings of the aforesaid