Browse Prior Art Database

SYNCHRONOUS AND ASYNCHRONQU$ WHITE LINE S KIPPING FOR FACSIMILE SYSTEMS

IP.com Disclosure Number: IPCOM000022885D
Original Publication Date: 1976-Mar-31
Included in the Prior Art Database: 2004-Mar-27
Document File: 4 page(s) / 647K

Publishing Venue

Xerox Disclosure Journal

Abstract

The transmitting terminal 11 and the receiving terminal 12 of the illustrated facsimile system are configured to carry out white line skipping, which is a redundancy reduction technique offering increased document transmission rates,

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

SYNCHRONOUS AND ASYNCHRONQU$
WHITE LINE S KIPPING FOR
FACSIMILE SYSTEMS
M. L~ Gorham
J~ D~ Torpie

Proposed Classification

U~S. Cl. 178/6

Int, Cl, H04n 7/00

The transmitting terminal 11 and the receiving terminal 12
of the illustrated facsimile system are configured to carry
out white line skipping, which is a redundancy reduction
technique offering increased document transmission rates,

At the transmitting terminal 11, a light beam is cyclically
scanned across a subject copy by a galvo mounted mirror 13
which is driven by a sweep generator 14 at a rate deter~
mined by an oscillator 15 and a frequency divider l6~ The

7J~DETECTOR'

-J

Volume 1 Nuraber 3 March 1976 4)

[This page contains 1 picture or other non-text object]

Page 2 of 4

SYNCHRONOUS AND ASYNCHRONOUS WHITE LINE SKIPPING FOR
FACSIMILE SYSTEMS (Contsd)

resulting information modulated light is converted into a
corresponding video signal by a photodetector 17, and the
video signal is then applied to a modulator 18. Addition-~
ally, a pulse generator 19 is triggered by the sweep gener~
ator 14 to supply synchronizing pulses which are timed to
coincide with the scan retrace, A feed mechanism 20
advances the subject copy a line at a time in response to
the synchronizing pulses, and those pulses are also
applied to the modulator 18. Accordingly, the modulator
18 supplies a carrier signal which is modulated in accor~
dance with the video signal and the synchronizing pulses,
and the modulated carrier is then transmitted to the
receiving terminal 12 via a communications link 21 provided
by, say, the public switched telephone network,

Upon reaching the receiving terminal 12, the carrier signal
is demodulated by a demodulator 22 to recover the video
signal and the synchronizing pulses. The video signal
drives a printer 23 which prints the facsimile copy on a
recording medium which in turn is advanced a line at a
time by another feed mechanism 24 under the control of
the synchronizing pulses.

To carry out white line skipping, the transmitting terminal
11 comprises a black detector 25 for monitoring the video
signal generated by the photodetector 17 and a controller
26 which is reset on a line-by~linebasis by the sweep
generator 14 to determine from the output of the detector
25 whether successive lines of the subject copy contain
meaningful information or not, Scanning of the subject
copy progresses at a normal rate, until a line without any
meaningful information (i.e....