MHV connector
The MHV (miniature high voltage) connector is a type of RF connector used for terminating coaxial cable. The connector looks almost identical to a typical BNC connector, but is not designed to mate with BNC jacks. MHV connectors can be recognized by the slightly protruding insulation on the male plug and the slightly different insulation length in the female jack. Despite these design differences, MHV and BNC plugs and jacks can be made to mate by brute force. This causes safety hazards, since a user can accidentally (or deliberately) mate a low voltage cable to a high voltage jack, (although in a correctly made MHV connector the pin is further back in the insulator than on BNC so theoretically they should never be able to make contact when used with BNC)
The MHV connector is typically rated for 5000 volts DC and 3 amperes. It was commonly used in laboratory settings for voltages beyond the rating of BNC connectors and for Geiger counter and scintillation probes, which commonly employ 500 to 1000 volts or more.
MHV connectors are presently considered by some as a safety hazard because of the possibility of high voltage on the exposed central pin when not plugged in,[1] and because the ground connection is broken before the power connection when demating. SHV connectors are designed to prevent these hazards, and cannot be mated to BNC connectors.