A pin-and-socket type reversing plug connector for three-phase alternating current motors has three phase pins and two internally connected ground pins in a motor-connected member and corresponding sockets in a line-connected member. The five pins and sockets are arranged in a straight line, with a phase...http://www.google.co.uk/patents/US4258969?utm_source=gb-gplus-sharePatent US4258969 - Reversing plug connector
