Monitoring apparatus and control apparatus for traffic signal lights

A control apparatus for traffic signal lights incorporating an illumination control circuit for controlling the illumination of signal lights of respective signal light units installed at an intersection where several roads intersect, said control apparatus comprising:

• a signal light monitoring circuit provided with, sensor means for detecting an illumination condition of respective signal lights, and judgment means for generating an output of logic value 1 corresponding to a high energy condition indicating a normal condition of the signal lights when, based on an output from said sensor means, the number of illuminated or non-illuminated signal lights is a predetermined number, and generating an output of logic value 0 corresponding to a low energy condition indicating an abnormal condition of the signal lights when the number is not the predetermined number;
• and
• a signal light power supply control circuit which supplies power to the signal lights when an output of logic value 1 is generated from said signal light monitoring circuit, and which stops power supply to the signal lights when an output of logic value 0 is generated;
• wherein said signal light monitoring circuit comprises:
• sensor means constructed so as to generate an AC signal at the time of non-illumination of a signal light, and not to generate an AC signal at the time of illumination;
• and
• judgment means which generates an output of logic value 1 when the number of non-illumination outputs from said sensor means is a predetermined number, and generates an output of logic value 0 indicating a signal light simultaneous illumination fault where simultaneous illumination is not permitted, when not the predetermined number;
• wherein said signal light power supply control circuit has an electromagnetic relay having relay contact points disposed in series in the power supply lines for the respective signal lights, the construction being such that said electromagnetic relay is placed in a non-excited condition with said contact points open, based on an output of logic value 0 indicating simultaneous illumination from said signal light monitoring circuit;
• and
• wherein said signal light power supply control circuit incorporates:
• a first self-hold circuit with a signal light power source switch on signal as a trigger input signal, and an output from said signal light monitoring circuit as a reset input signal, which self-hold said trigger input signal,
• the construction being such that said electromagnetic relay is excited and the contact points thus closed with an output of logic value 1 from said first self-hold circuit when a reset input signal of logic value 1 indicating normal signal lighting from said monitoring circuit, and a trigger input signal of logic value 1 due to said power source switch on signal are input together.