<P> Holedall IX internally expanded (internally swaged) hose coupling is used in higher pressure applications, or where the hose is exposed to higher end pull, or where a full flow is required . They are installed with special hydraulic drawbar machinery, using special pull plugs . </P> <P> National Hose thread (NH), also known as National Standard Thread (NST). It is the most common type of fire hose coupling used in the United States . The male and female straight (non-tapered) threads screw together and the connection is sealed with a gasket . </P> <P> The type of threaded coupling with a pin - lug swivel used on fire hoses was first manufactured prior to 1873 in the U.S.: </P> <Ul> <Li> Unknown patent by Charles W. Emery, dated July 11, 1865, </Li> <Li> 1874: Hose - Couplings, No. 149,029 by W.A. Caswell </Li> <Li> 1874: Hose - Couplings, No. 149,441 by W.A. Caswell, describes a method of casting the hose tail inside the coupler, so that it can pivot but not be detached . </Li> <Li> 1876: HOSE - COUPLING, No. 175,232 . </Li> </Ul>

Which type of hose coupling does not have male or female ends