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Class Information
Number: 181/18
Name: Acoustics > Speaking tubes > Systems
Description: Construction of speaking-tubes with their associated parts; also "speaking-tube exchanges", also, any patents on speaking-tubes not classified elsewhere.

Patents under this class:

Patent Number Title Of Patent Date Issued
7525440 Person monitoring Apr. 28, 2009
5209226 Underwater respiratory device May. 11, 1993
4932495 Vocal sound muffling device Jun. 12, 1990
4926961 Hinged acoustical voice tube May. 22, 1990
4839871 Underwater communication device Jun. 13, 1989
4527658 Bubble silencer for an underwater voice communicator Jul. 9, 1985
4527657 Tapered tube impedance matching underwater voice communicator with bubble silencer Jul. 9, 1985
4505358 Voice communicator Mar. 19, 1985
4473130 Crash helmet with communication system Sep. 25, 1984
4472607 Inflight headset for civil aircraft Sep. 18, 1984
4183422 Underwater communications device Jan. 15, 1980
4174155 Sound absorbing article and methods of constructing and utilizing same Nov. 13, 1979

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