Specifications
Print2CAD OCR 2013- 109
Print2CAD
OCR 2013
17.3.2 G3, G4 Compression
“Group 3 and 4 faxes are digital formats, and take advantage of digital compression
methods to greatly reduce transmission times. Group 3 faxes conform to the ITU-T
Recommendations T.30 and T.4. Group 3 faxes take between six and fteen seconds to
transmit a single page (not including the initial time for the fax machines to handshake
and synchronize). Group 4 faxes conform to the ITU-T Recommendations T.563, T.503,
T.521, T.6, T.62, T.70, T.72, T.411 to T.417. They are designed to operate over 64 kbit/s
digital ISDN circuits. Their resolution is determined by the T.6 recommendation, which
is a superset of the T.4 recommendation.
Fax Over IP (FOIP) can transmit and receive pre-digitized documents at near realtime
speeds. Scanned documents are limited to the amount of time the user takes to load the
document in a scanner and for the device to process a digital le. The resolution can vary
from as little as 150 DPI to 9600 DPI or more. This type of faxing is not like the e-mail
to fax service that still uses fax modems.
Group 3 fax machines transfer one or a few printed or handwritten pages per minute in
black-and-white (bitonal) at a resolution of 204×98 (normal) or 204×196 (ne) dots per
square inch. The transfer rate is 14.4 kbit/s or higher for modems and some fax machines,
but fax machines support speeds beginning with 2400 bit/s and typically operate at 9600
bit/s. The transferred image formats are called ITU-T (formerly CCITT) fax group 3 or 4.”
Source: Wikipedia, subject “G4 Compression”
License Agreement: http://creativecommons.org/licenses/by-sa/3.0/
17.3.3 JPEG Compression
“The JPEG compression algorithm is at its best on photographs and paintings of realistic
scenes with smooth variations of tone and color. For web usage, where the bandwidth
used by an image is important, JPEG is very popular. JPEG/Exif is also the most common
format saved by digital cameras.”
Source: Wikipedia, subject “JPG Compression”
License Agreement: http://creativecommons.org/licenses/by-sa/3.0/