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Sec. 8–9 Television 637
pulses. The remainder of the block diagram is self-explanatory. The user-available adjustments
for an analog black-and-white TV are also shown.
MTS Stereo Sound
Stereo audio, also known as multichannel television sound (MTS), is also available and is
accomplished using the FDM technique shown in Fig. 8–33. This FDM technique is similar to
that used in standard FM broadcasting, studied in Sec. 5–7 and illustrated by Fig. 5–18. For
compatibility with monaural audio television receivers, the left plus right audio, m L (t) + m R (t),
is frequency modulated directly onto the aural carrier of the television station. Stereo capability
is obtained by using a DSB-SC subcarrier with m L (t) - m R (t) modulation. The subcarrier
frequency is 2f h , where f h = 15.734 kHz is the horizontal sync frequency for the video. (See
Table 8–12.) Capability is also provided for a second audio program (SAP), such as audio in a
second language. This is accomplished by using an FM subcarrier of frequency 5f h .
Furthermore, a professional channel subcarrier at 6.5f h is allowed for the transmission of voice
or data on a subscription service basis to paying customers. For further details on the FDM
aural standards that have been adopted by television broadcasters and for other possible FDM
formats, see a paper by Eilers [1985].
Analog Color Television
Color television pictures are synthesized by combining red, green, and blue light in the
proper proportion to produce the desired color. This is done by using a color display that
has three types of pixels: one type that emits red light, one that emits green light, and a third
type that emits blue light. Therefore, three electronic video signals—m R (t), m G (t), and
|M a (f)|
Spectrum of m L (t)+ m R (t)
Pilot tone
Spectrum of DSB-SC stereo
subcarrier with m L (t) – m R (t) modulation
SAP FM subcarrier
Professional
subcarrier
0
f h 2f h 3f h 4f h 5f h 6f h 7f h
6.5f h
Figure 8–33 Spectrum of composite FDM baseband modulation on the FM
aural carrier of U.S. analog TV stations.
f