Device having light transmission means

A device (1) having a light transmission means wherein a light-emitting element (3), a driving circuit for driving this light-emitting element (3), a light-receiving element (light-detecting element) (5), a light-guiding path (wave-guiding path) (4) for guiding light from the light-emitting element (3) to the light-receiving element (5), an amplifying circuit 6, wiring (electric wiring) (7) and a circuit (8) are successively provided on a substrate (2). The light (light signals) from the light-emitting element (3) passes through the light-guiding path (4) and is received at the light-receiving element (5), transferring photoelectricity. The electric signals from the light-receiving element (5) are amplified at the amplifying circuit (6) and are input to the circuit (8) through the wiring (7). The circuit (8) operates based on these electric signals.