| 摘要 |
PURPOSE:To shorten the light emission time of an LED and to reduce the power consumption by employing a differential modulation system. CONSTITUTION:When data are sent, a serial input/output interface 7 is controlled by a CPU to output serial data to a differential modulating circuit 9. The differential modulating circuit 9 generates a pulse which rises momentarily every time the serial signal varies between '1' and '0', the light emitting element emits light instantaneously with the pulse signal, and the light is projected as a light signal on a opposite side. A light receiving element, on the other hand, receives and converts the light incident from the opposite side photoelectrically and a pulse signal is obtained through a light receiving circuit 15 and converted by a demodulating circuit 16 into a serial signal of the same form with the transmission side; and the signal is inputted to the serial input/ output interface 7 and read in a CPU. In this transmission and reception system, the LED as the light emitting element emits the light only the moment the serial signal varies between '1' and '0' and its power consumption is small. |
