To easily constitute a system for executing the interlocked control of power supply on/off for a master device and a slave device.

A power supply input part 4 for a personal computer 1 to be a master device is connected to a power supply ON/OFF interlocking circuit 3 built in an window ticket issuing terminal equipment 2 to be a slave device and the interlocking circuit 3 connected to an external power source 6 through a power supply input part 5 supplies power to the computer 1, detects the power supply on/off of the computer 1 and controls the power supply on/off of the terminal equipment 2 interlocking with that of the computer 1.