Patent ID: 8271808

Claim:
A computer system including a main device and a subordinate device connected mutually by means of an optical transmission system, the main device comprising: a main-device-side light reception determination part determining presence or absence of light reception from the subordinate device; and a main-device-side power supply control part controlling a power supply operation of the main device at least based on a determination result by the main-device-side light reception determination part, the subordinate device comprising: a subordinate-device-side light reception determination part determining presence or absence of light reception from the main device; and a subordinate-device-side power supply control part controlling a power supply operation of the subordinate device at least based on a determination result by the subordinate-device-side light reception determination part, wherein the main-device-side power supply control part turns on a power supply of the main device when a manual power supply turning-on operation has been performed to the main device and the main-device-side light reception determination part determines presence of light reception from the subordinate device, and the subordinate-device-side power supply control part cuts off a power supply of the subordinate device when a manual power supply cutting-off operation has been performed to the subordinate device and the subordinate-device-side light reception determination part determines absence of light reception from the main device.