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OPTIONS
Active Subwoofer
Comb FilterCF700
SVM module
Audio FeatureAR700
Audio FeatureAR701
Adjustable AudioTA700
Scart 3 + VGA-audioTA710
Scart 3TA711
Picture in PicturePP700 / 710
Active Subwoofer
GeneralFunctional description
The active subwoofer system provides a clear improve-Depending on the standard, the module either bypasses
ment in stereo sound. The system consists of active filters,or filters the input signal as follows:
power amplifiers, a subwoofer, and stereo speakers. The
active subwoofer stage is designed to be used with an in-PAL and NTSC 3.58
ternal subwoofer box and stereo speakers in the TV set orThe signal is fed to comb filter IC and separated
with small external front speakers.for Y and C signals
Functional descriptionNTSC 4.43 and SECAM
The left and right stereo channels are already added to-The signal is fed to comb filter IC, but it is not sepa-
gether in the sound processor MSP3410D. The sound proc-rated
essor also includes the required lowpass filters for the
subwoofer channel and highpass filters for the loudspeakerS-VHS The signal is bypassed in the multiplexer IC
channels.
The signal is taken from sound processor pin 31 and fedThe standard is identified in the colour decoder Icd1. The
onward to the high pass filter (40 Hz), consisting of transis-standard information is input to the microcontroller via the
tor ta6 and associated components.IIC-bus and back to the colour decoder again. The infor-
The filtered signal is then fed to the audio power amplifier,mation is output from pin 23 to comb filter module pin 1,
ICa4. The amplifier can be muted by pulling pin 2 low. Thefrom pin 16 to module pin 2, and from pin 15 to module
mute control signal is taken from microcontroller (pin 51)pin 13.
via transistors ta10, ta4 and ta5. This mute function mutesModule pin 1 controls the multiplexer to bypass the video
each of the audio power amplifiers in the set. However,signal (OL�) or to feed the signal to the comb filter IC (OH�).
the subwoofer amplifier can also be muted separately. ThisWhen pin 1 is high, it inputs the colour subcarrier frequency
can be done via the audio processor. A high level on pin 5(Fsc) to an internal clock generator of the comb filter IC.
drives transistor ta5 to conduct, which just mutes theModule pin 2 defines the comb filtering method, PAL (OL�)
subwoofer amplifier. Due to the resistor network ra106,or NTSC 3.58 (OH�).
ra105 and ra14, the central mute will be not activated inModule pin 13 drives the comb filter IC to be in comb filter-
this case.ing mode (OH�), at which time the IC performs Y / C sepa-
The amplifier operates in a bridge configuration. The out-ration. Or to be in a bypass mode (OL�), whereat the signal
puts are internally inverse feedback connected to the in-is not separated, but fed only via an internal delay stage.
puts of each other. The amplified, phase opposition sig-In addition, pin 13 informs the colour decoder the exist-
nals are output from pins 4 and 6 to the subwoofer speaker.ence of the module by transistor tc3 (base-collector joint).
Depending on which standard is in use, the logical high /
Comb Filter module, CF700low level combinations are as follows:
GeneralStandardmodulemodulemodule
The basic function of the comb filter is to separate the lu-pin 1pin 2pin 13
minance (Y) and chrominance (C) signals from the CVBS
PALOHO + 4.43OL�OHO
signal. The device minimizes problems caused during Y /NTSC 3.58OHO + 3.58OHOOHO
C separation such as dot-crawl and cross colour interfer-NTSC 4.43OHO + 4.43OL�OL�
ence. In addition, it allows the input video signal to haveSECAMOHO + 4.28OL�OL�
an extended frequency bandwidth. This is carried out us-
ing a clock frequency of four times the colour subcarrierS-VHSOL�OL�OL�
frequency. The filter is capable of handling signals accord-
ing to the PAL and NTSC 3.58 standards. The module con-
tains two ICs, the multiplexer circuit, icc1 and the comb
filter circuit, icc2. |
ACEC
