Gestetner B147, Service Manual

Page: 628 / 1081

ORIGINAL SIZE DETECTION
B597 18 SM
4.3.2 MIXED ORIGINAL SIZE MODE
This section explains what happens when the user selects mixed original size
mode.
Because this ADF is a sheet-through document feeder, the method for original
document width detection is the same as when the originals are the same size, but
the document length detection method is different. Therefore, the scanning speed
is slightly slower.
Document length detection
From when the registration sensor switches on until the interval sensor switches
off, the CPU counts the transport motor pulses. The number of pulses determines
the length of the original.
Feed-in cycle
When the original size for the copy modes listed below cannot be determined, the
image cannot be correctly scaled (reduced or enlarged) or processed until the
document length has been accurately detected. The length must be determined
before the image is scanned.
Auto Reduce/Enlarge
Centering
Erase Center/Border
Booklet
Image Repeat
An original follows this path during transport:
1. Document length detection
!
Scanning glass
!
Inverter table
2. Inverter table
!
Scanning glass
!
Inverter table (restores original order)
3. Inverter table ! Scanning glass (image scanned) ! Exit tray
Normal feed-in
In a copy mode other than those listed above, when the rate of
reduction/enlargement has been determined, the originals are scanned normally. In
order to store the scanned images, a large area of memory (the detected document
width x 432 mm) is prepared. Next, only the portion of the image up to the detected
document length is read from memory and printed.