Abstract: An electrical circuit assembly is provided for monitoring the flow of particulate fuel material in a chute having window areas on opposite sides thereof. The circuit assembly emits a light at one window end of the chute which is received at the opposite window end of the chute by a circuit assembly. The condition of the received light is dependent upon fuel material flow in the chute. If the flow is normal the emitted light will be intermittently interrupted by the particulate material resulting in chopped light being received by the circuit. If the chute is blocked downstream the chute will be filled with material and there will be no light received by the circuit. Similarly, if the blockage is upstream the chute will be empty and an uninterrupted light will be received. The circuit analyzes these received light conditions and produces output signals indicative of the mentioned fuel flow conditions.