The term BNC comes from the type of connector and the inventor's names - Bayonet Neill-Concelman (BNC). Paul Neill of Bell Labs was a major influence, Concelman worked at Amphenol. They were working on a military connector that was simple to use. The connector is referenced in MIL-STD-348. Typically the male connector is fitted to a cable, and the female to a panel on equipment. They are usually applied for frequencies below 4 GHz and voltages below 500 volts. The design was patented in 1951. BNC connectors are most commonly made in 50 and 75 ohm versions, matched for use with cables of the same characteristic impedance.