3 Pin Small Size Chassis Male Cannon Type Connector

The Standard is defined by the Audio Engineering Society inAES14-1992(r1998)
Pin 1: Shield/Ground
Pin 2: Hot/in Phase / +
Pin 3: Cold / Out of Phase / -
To create an unbalanced connection, pin 1 & pin 3 are connected to ground & pin 2 carries the signal. Note that there is a lot of equipment (particularly in the US) that has pin 2 & pin 3designations reversed (i.e. 3 hot, 2 cold).Manufacturers are adopting the Standard on all new equipment.