Signal conversion system converts slow-scan video signals into standard fast-scan television signals that are required for reproduction of television pictures on American TV sets. This system permits conversion of TV pictures produced in accordance with the standards of one country into the standards of another country

Lipoma, P. C.

Te Poel, H. E.

English

NASA Technical Reports Server

December 1969
	
Brief 69-10748 
NASA TECH BRIEF 
-------------
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151. 
System Converts Slow-Scan to Standard 
Fast-Scan TV Signals 
30rps	 Motor 
'an Slow Scan Standard F.M. L 4  TV Amp Osc Mod Amp — —	 Camera Monitor
Standard Magnetic Storage	
' Limiter 
Sync Record Gate-..	 Disk 
Generator 31.5 kHz - - - 
60 Hz FM 
^ 32 FIF Demod 
1.008 MHz
eset
^ 6 ^ 5	 FF
Output 
Amplifier 
VCO	 Phase SS Det V
Standard  j AND TV 3.2 kHz Monitor
 Sync. 
________	
SS __________ 
Separator I  
Slow Scan I	 .
J	
Reset 
Video Input Hz 
Integrator 
The system shown in the block diagram has been 
developed to convert slow-scan video signals (trans-
mitted from a special TV camera) into standard fast-
scan television signals that are required for repro-
duction of television pictures on American TV sets. 
This system is specially designed to convert slow-scan 
video signals transmitted from the Apollo tele-
vision equipment into the required fast-scan TV for-
mat. Each TV image or frame from the Apollo equip-
ment is composed of 320 horizontal lines, and the 
frames are formed at a rate of 10 per second in a non-
interlaced manner. In the standard TV broadcast 
system used in this country, each complete picture 
frame is composed of 525 horizontal lines, and 30 
complete frames are generated per second using a 2:1 
interlacing technique. Although specifically developed 
for the Apollo application, the new system can be 
readily modified to accept different slow-scan TV 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the Uniteø States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19690000647 2020-03-16T18:34:41+00:00Z
formats, including European slow-scan rates, for con-
version to the standard U.S. TV broadcast format. 
The new system, modified with adjustable circuit ele-
ments, will eliminate many of the difficulties associated 
with other systems used for converting TV pictures 
produced in accordance with the standards of one 
country into TV signals conforming to the standards 
of another country. 
In describing the system with reference to the block 
diagram, the term "frame" refers to the picture image 
or video signal produced during one vertical scanning 
interval regardless of whether an interlaced or a non-
interlaced technique is used. The slow-scan monitor, 
which receives the incoming slow-scan video signals, 
reproduces on its CRT display screen the TV pictures 
corresponding to these signals. For the slow-scan, non-
interlaced signal of 320 lines per frame and 10 frames 
per second, the electron beam in the CRT of the slow-
scan monitor traces out the horizontal lines of the 
picture at a rate of 3200 lines per second. An electron 
image of the slow-scan monitor picture is produced on 
the target structure within the standard broadcast TV 
camera which is focused on the display screen of the 
slow-scan monitor. This target structure is scanned 
line-by-line by the electron beam contained in the 
camera to generate a video output signal correspond-
ing to the monitor picture being viewed by the camera. 
The standard broadcast-type of sync generator con-
trols the scanning process in the camera. This scan-
ning is performed (in this case) in accordance with the 
U.S. standard of 525 horizontal lines per complete 
picture and 30 complete pictures per second with 2:1 
interlacing. Because of the 2:1 interlacing, the elec-
tron beam in the standard TV camera moves from 
the top to the bottom of the image at a rate of 60 times 
per second, and during each such scan traces out a 
series of 262.5 lines. Thus the sync generator supplies 
to the camera 12 vertical scanning signals at a fre-
quency of 60 Hz and horizontal scanning signals at a 
frequency of 15.75 kHz. The generator also supplies 
to the camera the usual synchronizing and blanking 
pulses. The slow-scan monitor, running at a vertical-
scanning frequency of 10 Hz, takes 0.1 second to build 
up a complete picture; on the other hand, the camera, 
running at a vertical-scanning frequency of 60 Hz, 
can completely scan a complete image in 1/60 second. 
Thus the camera scans at 6 times the speed of the slow-
scan monitor. 
If the camera were allowed to generate a continuous 
output signal in its normal manner and if such signal 
were applied to a TV set or monitor, the successive 
images reproduced on the TV screen would be com-
posed of varying proportions of earlier and later slow-
scan frames. In order to prevent this from occurring, 
the vertical scanning action of the camera is locked in 
step with the vertical scanning action of the slow-scan 
monitor, so that one of every six vertical scans in the 
camera constitutes a scanning of a single complete 
frame or picture on the display screen of the slow-
scan monitor. Therefore every sixth camera scan is 
used to provide the desired fast-scan TV signal. This, 
however, leaves a time gap of 5/60 second (5 camera 
vertical-scan intervals) between the successive usable 
fast scans of the camera. To fill in these gaps, each 
usable fast-scan signal portion is stored on the disk 
of a magnetic recorder. This recorder then plays back 
•the usable fast-scan signal five times, and these re-
peated signals are used to fill in the time delay between 
the original fast-scan signal and the next usable fast-
scan signal. The fast-scan TV signal thus obtained will 
produce continuous TV pictures on conventional TV 
sets or standard TV monitors. The resulting pictures 
will have a pleasing and entirely normal appearance, 
except for scenes having fast-moving objects. In the 
latter case, the movement will appear to occur in short, 
quick jumps instead of in a smooth, continuous man-
ner. This movement, however, has only a relatively 
slight effect on the appearance of the scene to the 
viewer. 
The continuous, interlaced standard TV broadcast 
signal from the output amplifier can be supplied 
to standard TV sets or monitors at various remote 
locations by means of an appropriate signal distri-
bution system. It can also be supplied to a TV trans-
mitting station for further broadcasting. 
Notes: 
1. Magnetic tape recording and playback equipment 
for the scan-rate conversion of TV signals is de-
scribed in Tech Brief 67-10676. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: TSP69- 10748 
Patent status: 
This invention is owned by NASA, and a patent

application has been filed. Royalty-free, non-exclusive

licenses for its commercial use will be granted by

NASA. Inquiries concerning license rights should be

made to NASA, Code GP, Washington, D.C. 20546.

Source: H. E. TePoel

NASA-Manned Spacecraft Center

and P. C. Lipoma of

Lockheed Electronics Corporation

(MSC-90534)
. 
. 
Brief 69-10748	 Category 01


System converts slow-scan to standard fast-scan TV signals

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