Based on reading rate of between 500-1000 words/minute, transmitting typewritten matter only, system uses lowest possible bandwidth to avoid overcrowding, while furnishing data as fast as it can be absorbed by pilot. Bandwidth requirements are less than 150 kHz, a considerable saving over conventional television

Brown, R. L., Sr.

English

NASA Technical Reports Server

1972	 B72-10139 
NASA TECH BRIEF 
Marshall Space Flight Center	
_4V 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Aircraft Communication Via Telefacsimile System 
Ground control communications to aircraft in the 
vicinity of large airports is a major problem. These prob-
lems are increasing with the progressive growth of air 
traffic. Present communications, being largely voice, are 
subject to misinterpretation, misunderstanding, and inter-
ference to an intolerable degree. 
The advancement of electronic components is at a 
point where telefacsimile systems are now feasible. Such 
a system, providing a written and pictorial means of 
communicating with approaching aircraft, would lessen 
the work load on ground control crews. 
This system would use as low a bandwidth as possible 
to avoid overcrowding, while furnishing data as fast as it 
can be absorbed by the pilot. The proposed system is 
based on a reading rate of between 500-1000 words/ 
minute, transmitting typewritten matter only. At a rate 
of 34 lines/second, 200 lines/inch will provide full scale 
(1:1) typewritten matter at 10 inches/minute, which 
meets the criteria of the system and is readable. Band-
width requirements based on 8 inch wide lines of written 
matter are less than 150 kHz, a considerable saving over 
conventional television. 
A conventional flying spot scanner, moving from left 
to right at uniform rate, scans materials repetitively; the 
material moving forward one line space between scans. 
A mechanical feed, based on a stepping motor-drive, will 
accomplish this using the spot scanner retrace pulse to 
trigger each step. The output signal is a line of video 
carrying a synchronizing pulse at the end of each line.
There is automatic synchronization to any portion of any 
signal transmitted, either the top, middle, or bottom of 
a page; however, elaborate synchronization schemes, 
used in television, are not required. 
The receiver is connected to a cathode ray tube, de-
signed to produce a single, high intensity modulated line. 
The line "writes" on a strip of sensitized paper or plastic, 
of which several varieties are suitable. The strip is fed 
over the face of the cathode ray tube by a stepping 
motor drive, duplicating the scanner drive mechanism. 
The synchronizing pulse at the end of each line of video 
is used to trigger the stepping motor. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Code A & TS-TU 
NASA - MSFC 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B72-10139 
Patent Status: 
No patent action is contemplated by NASA. 
Source: R. L.. Brown, Sr. of
Marshall Space Flight Center
(MFS-20839) 
S
Category 02 
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Aircraft communication via telefacsimile system

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