Jam Sensors - Ricoh FT5540 Service Manual

7.5 Jam Sensors

The jam sensor detects misfeeds of paper in the sorter.
The LED on the lower jam sensor board is turned on by a pulse signal which is supplied by an
oscillator.
This pulse signal detection system has an advantage over a photointerruptor system because
there is no noise from external light.
When there is no paper between the upper and the lower jam sensors, the LED on the lower
jam sensor board activates a photransistor (PTr1) on the upper jam sensor board. PTr1 turns
on Q3, which causes IC1 pin 6 to have a higher voltage than pin 7. IC1 pin 1 then goes LOW.
IC2 pin 4 is then lower than pin 5, causing pin 2 of IC2 to output HIGH. This HIGH signal at
CN123-2 informs the sorter main board that no paper is present.
When paper is entering a bin, the phototransistor (PTr1) turns off. This causes the circuit to
output a LOW signal to CN123-2. The sorter main board determines that paper is in the bins.
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31 August 1989