Sony HXC-100 Service Manual page 19

Prompter Signal
This signal is sent to the MPEG2 decoder on the ENC-112 board for decoding.
In the case of the VBS prompter, the decoded signal is output from the VBS encoder (IC1201) on the
CD-61 board to the SY-363 board.
In the case of the HD prompter, the decoded signal is sent to the DPR-298 board.
ENC-112 Board
This small board is mounted on the CD-61 board, and compresses/decompresses the video signal for
prompter.
IC100 functions for MPEG2 encoding and decoding, but is used only for decoding in this unit.
Signal Transmission Block
TX-126 Board
This board consists of a OFDM signal transmitter/receiver circuit for transmission of the video signal,
audio signal, intercom signal, and commands, and an FM modulation/demodulation circuit for transmis-
sion of the standby intercom signal, synchronizing signal, and TONE signal.
OFDM Signal Transmitter/Receiver Circuit
The OFDM signal output consists of six waves F1 to F6 to transmit video, sub video, microphone, inter-
com, and command signals.
The OFDM signal transmitter, consisting of two systems: LOW band (F1 to F3) and MID band (F4 to F6),
amplifi es the OFDM signal generated by the D/A converter on the CD-61 board independently for each
band. The LOW band signal is mixed with the 1.4 MHz FM-modulated signal and is combined with the
MID band signal in the MPX fi lter (FL601), and then the composite signal is output to the CCU.
The OFDM signal input consists of three waves F7 to F9 to transmit return video, prompter video, inter-
com, PGM, and command signals.
The OFDM signal receiver that is composed independently for F7 to F9 amplifi es the waves F7 to F9
output from the HPF of the MPX fi lter (FL601), selects them by band with the BPF (FL301, FL401, and
FL501), and then processes them.
The level of each signal selected by band is regulated by the step gain amplifi er that automatically switch-
es amplifi er gain to four steps according to the input level and by the AGC amplifi er (IC302, IC402, and
IC502), and then the center frequency of F7 to F9 is converted to 36 MHz by the MIXER IC (IC303,
IC403, and IC503). The converted OFDM signal is converted to TS data by the demodulator ICs (IC603,
IC604, and IC605), and then the serial data is output to the CD-61 board.
FM Modulation and Demodulation Circuits
The FM modulation circuit mixes the standby INCOM signal (STB INCOM TO CCU: CHU → CCU)
and the TONE signal (16.38 kHz), modulates (FM) the mixed signal with a carrier frequency of 1.4 MHz,
and then sends the signal to the CCU.
In the FM demodulation circuit, the FM signal (that is modulated with 1.0 MHz carrier frequency) is
extracted from the RF signal sent from the CCU by the MPX fi lter (FL601) and the BPF (FL2), and the
FM signal is demodulated to a standby INCOM signal (STB INCOM FR CCU: CCU → CHU) and a
synchronizing signal by the demodulator (IC13 LA2135M).
The demodulated standby INCOM signal is output by the output amplifi er at a signal level of 220 mVp-p
(0 dBu input). The synchronizing signal waveform is shaped, and the signal is output with an amplitude of
3.3 Vp-p.
The 1.0 MHz FM-modulated wave is detected by IC16 to check the presence of an FM signal wave.
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HXC-100/V1 (E)