Abstract: A vehicle trailer male electrical connector 10, especially for use with a vehicle tracking or data logging system and which having an array of connector pins 11-17 for interconnecting electrical power between a vehicle trailer and tractor unit, and which includes an electrical switch 43 in an open or closed condition, and which is changed to the other of said open and closed conditions by engagement with a female connector on a tractor unit. The switch 43 is operated by one of said connector pins 11-17 which is axially displaceable on contact with the female connector.