Abstract: A terrorist vehicle barrier is disclosed having high strength cables stretched between two vertical I-beams. The cables are attached to the I-beams in a unique shock absorbing arrangement. The barrier is actuatable from a position below ground to effectively arrest the motion of a high speed terrorist vehicle. Various means are disclosed for actuating the gate. The barrier is designed to solve esthetic problems encountered in making a building secure from terrorist attack as well as to be strong enough to stop a high speed vehicle with minimum damage to the barrier, the vehicle, or the vehicle driver.

Abstract: An underwater voice communicator in which the preferred embodiment comprises a pair of tapered tubes in communication with a diver's mouth. The tubes are constructed of a material having a sound impedance similar to the sound impedance of water. Sound energy issuing from the mouth of a diver is reflected down the length of the tapered tubes to an area of the tube that concentrates the sound for injection into the surrounding water.

Abstract: A bubble silencer for use with scuba equipment is comprised of a flat flexible enclosure attached to a scuba regulator valve. Exhaust bubbles issuing from the regulator into the enclosure coalesce into large air parcels to be expelled at low velocity through a rearward exit port. The large size and low velocity of the exhaust bubbles leaving the enclosure are much quieter than the small high velocity bubbles issuing from the regulator itself.