Paper Size Board - Ricoh FT7770 Service Manual

30
April, '89

Paper Size Board

9.
The paper size sensor board is located on the bottom of the paper tray.
Paper size detection circuit operation begins with the application of +15
volts to the photointerrupters.
For the photointerrupters that do not
have a shutter present, the LEDs activate the phototransistors. The main
board signal lines connected to the active phototransistors then go HIGH.
If a shutter is present, the phototransistor will be off and the main board
signal line will go LOW. The combination of HIGH and LOW signals deter-
mine paper size and scanner return timing.
The following table shows the relationship between the paper size and sig-
nal combination.
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