BNC connectors are commonly used for RF connections, ham radio antenna connections, avionics, electronic test equipment and video signals. They were frequently also used as an alternative to the RCA connector. The acronym BNC means "Bayonet Mount Neill Concelman". Concelman and Neill were the inventors responsible.
BNC connectors were originally only available in 50 ohms, but are now also available in 75 ohms. They can be typically used at frequencies up to 4 and 2 GHz.
A TNC connector is a threaded version of the BNC connector used in a wide range of radio and wired applications. Currently, a common use is WI-fi routers made by Linksys and audio equipment. The acronym TNC means "Threaded Neill-Concelman" and is named after the inventors: Carl Concelman or Amphenol and Paul Neill of Bell Labs.
The connector usually has a 50 ohm impedance and operates best in the 0–11 GHz frequency spectrum. It has better performance than the BNC connector at microwave frequencies.