that525ch THAT Corporation, that525ch Datasheet
that525ch
Manufacturer Part Number
that525ch
Description
Dbx-tv Noise Reduction Systems
Manufacturer
THAT Corporation
Datasheet
1.THAT525CH.pdf
(2 pages)
T H A T
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cast-quality circuit boards originally developed to
conveniently implement the dbx-TV noise-reduction
portion of the BTSC Multichannel Television Sound
system. In a properly designed modulator, the
cards offer performance exceeding FCC require-
ments for separation, dynamic range, frequency re-
sponse and distortion of BTSC signals. Based on a
highly effective combination of wideband and spec-
tral companding algorithms, the system is also ap-
plicable to any analog or digital audio channel with
an uncompanded signal-to-noise ratio as low as
26dB.
Basic Operation
dynamic range of the program audio before trans-
mission, and then expanding the dynamic range
upon reception. In the compression cycle, a 2:1
(wideband) compression ratio is applied across the
entire audio spectrum while a spectral compressor
simultaneously varies the signal preemphasis
based on the high frequency content of the pro-
gram material. The spectrum of the resulting com-
pressed
provides optimal masking of channel noise in FM
transmission systems.
The THAT 525CH and 525EH cards are broad-
The dbx-TV system operates by compressing the
Unique Spectral Companding
System
Strong Noise Reduction (up to
50 dB)
Flat Frequency Response: Typ
+/-0.6 dB (Back-to-Back)
Low Distortion: Typ 0.1%
Excellent Subjective Quality,
Even With Very Noisy Channels
35 dB Midband Separation in
BTSC-TV Applications
signal resembles
FEATURES
THAT Corporation; 734 Forest Street; Marlborough, Massachusetts 01752; USA
Tel: (508) 229-2500; Fax: (508) 229-2590 Web: http://www.thatcorp.com
C o r p o r a t i o n
white noise,
dbx is a registered trademark of Carillon Electronics Corporation
DESCRIPTION
which
verted. The signal is expanded by a (wideband)
ratio of 1:2, while the spectral expander varies the
deemphasis to complement the compressor’s dy-
namic preemphasis characteristic. When program
signal is absent or low in level, channel noise is
thus drastically reduced. During higher level pas-
sages the 525 cards use the signal itself to effec-
tively mask channel noise
audio quality with a channel dynamic range as low
as 40 dB.
Compressors and Expanders
signals before transmission. It is typically used in
broadcast television and CATV transmitters to en-
sure the highest quality encoding possible. The
525EH is the complementary expander for decod-
ing signals after reception. It is typically used in
monitor receivers.
tion cards include reduced bit-rate digital encoders
and low-dynamic range analog transmission sys-
tems.
In the expansion cycle, the processing is in-
The result is a system which delivers CD-like
The 525CH is the compressor, used to encode
Other applications of the 525 Series noise reduc-
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Broadcast TV Modulators
Cable TV Modulators
BTSC Monitor Receivers
Satellite Communications
Terrestrial Microwave Links
Cable Transmission Links
Fiber Optic Links
Digital Encoders (A/D/A)
APPLICATIONS
dbx-TV Noise Reduction
THAT 525CH, 525EH
Systems
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that525ch Summary of contents
Page 1
... FM transmission systems. dbx is a registered trademark of Carillon Electronics Corporation THAT Corporation; 734 Forest Street; Marlborough, Massachusetts 01752; USA Tel: (508) 229-2500; Fax: (508) 229-2590 Web: http://www.thatcorp.com dbx-TV Noise Reduction THAT 525CH, 525EH APPLICATIONS • ...
Page 2
... See the EIA’s BTSC Recommended Practices for more details. 4. Response is given in deviation from the theoretical ideal curves for dbx-TV (BTSC) compression/expansion. THAT Corporation; 734 Forest Street; Marlborough, Massachusetts 01752; USA Tel: (508) 229-2500; Fax: (508) 229-2590 Web: http://www.thatcorp.com 1 ...