Browse Prior Art Database

WHITE LINE SKIPPING IN A FACSIMILE SYSTEM UTILIZING BWB ENCODING AND DECODING

IP.com Disclosure Number: IPCOM000022978D
Original Publication Date: 1976-May-31
Included in the Prior Art Database: 2004-Mar-27
Document File: 4 page(s) / 684K

Publishing Venue

Xerox Disclosure Journal

Abstract

A BWB (i.e., black-white-black) encoding format may be utilized in a white line skipping facsimile system employ- ing line-by-line synchronization, if provision is made for preventing the receiving terminal from printing in re- sponse to the synchronizing pulse received while white

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

WHITE LINE SKIPPING IN A
FACSIMILE SYSTEM UTILIZING

BWB ENCODING AND DECODING
R. N. Rivers
J. D. Torpie

Proposed Classification

U~S. Cl. 178/6
mt. Cl, H04n 7/00

~25

  STEP
'CONTROL

A BWB (i.e., black-white-black) encoding format may be

utilized in a white line skipping facsimile system employ-
ing line-by-line synchronization, if provision is made for
preventing the receiving terminal from printing in re-
sponse to the synchronizing pulse received while white

line skipping is taking place.

In the drawing, there is a facsimile system having a
transmitting terminal 11 comprising a galvo mounted mirror

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28

Volume 1 Number 5 May 1976 37

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

Page 2 of 4

WHITE LINE SKIPPING IN A FACSIMILE SYSTEM UTILIZING

BWE ENCODING AND DECODING (Cont~d)

12 which is driven by a sweep generator 13 at a rate deter-
mined by an oscillator 14 and a frequency divider 15 to
scan a light beam across a subject copy. That provides
information modulated light which is converted into a cor-

responding video signal by a photodetector 16, and the
video signal is then applied to a two to three-level black-
white-black encoder 17 and to a black detector 18,

A pulse generator 21 is triggered by the sweep generator

13 to provide synchronizing pulses which are timed to

coincide with the scan retrace. Those pulses are applied
to a feed mechanism 22 so that the subject copy is ad-
vanced one line for each scan and to a frequency modulator
23 which is also coupled to receive the three-level or
encoder video output of the encoder 16. Thus, the modu-
lator 23 supplies a carrier signal which is frequency

modulated in accordance with the encoded video and the
synchronizing pulses for transmission to a receiving

terminal 24 via a communications link 25 provided by, say,
the public switched telephone network,

At the receiving terminal 24, there is a demodulator 26
followed by a full wave rectifier 27 for recovering the

video signal and the synchronizing pulses. A printer 28
prints the facsimile copy on a recording medium which is
advanced by another feed mechanism 29 under the control of
the synchronizing pulses. To that end, the synchronizing

pulses are fed through a low pass filter 31 to a paper
advance detector 32 and to a sync recovery circuit 33,

Synchronous sampling pulses are applied to the paper
advance detector 32 by the sync recovery circuit to logi-

cally validate the synchronizing pulses, whereby a vali-
dated synchronizing pulse causes the detector 32 to
condition the feeder 29 to advance the recording medium
in response to a command supplied by the sync recovery

circuit 33 when the synchronizing pulse reaches a pre-
determined threshold level.

Scanning of the subject copy proceeds at a normal rate,
until a line with...