Process signal collecting apparatus

摘要

A process signal collecting apparatus comprises light transmitters (24, 25) for transmitting light pulses of the first and second wavelengths. These light pulses are transmitted through an optical fiber path (19) and light branches (401 to 416) to on/off optical switches (701 to 716). Each of the on/off optical switches is structured such that the light pulses of the first and second wavelengths are reflected therefrom when the same is in an on state while only the light pulse of the second wavelength is reflected when the same is in an off state. The reflected light pulses are detected by first and second light receivers (26, 27). A timing pulse is generated responsive to the reflected light pulse of the second wavelength. The presence or absence of the reflected light pulse of the first wavelength is discriminated as a function of the timing pulse, whereby an on state or an off state of each of the on/off optical switches is determined. The data of the decision thus obtained is stored in a memory (13) and is utilized by a central processing unit ( 1).