Panasonic VL-SV74BX, Service Manual

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4 Technical Descriptions
4.1 Block Diagram
The block diagram of Video intercom system is shown in Fig 4.1.
Image signal root:
The image data is converted into NTSC signal by Camera unit, and the NTSC signal is modulated into FM signal.
FM signal is sent to the Monitor station through the interphone cable with ASK signal which modulated from command signal
and voice signal. Demodulated NTSC signal is displayed on the LCD of Monitor station.
Route to Extention monitor:
The buffered FM signal is sent to the extention monitor through the interphone cable with ASK signal which modulated from
command signal and voice signal.
Demodulated NTSC signal is displayed on the LCD of Extention monitor.
Voice signal root:
The voice signal from the microphone of Door station is sent through the hybrid circuit(HYB), and interphone cable to the
speaker of Monitor station. While the voice from the microphone of Monitor station reaches the speaker of the Door station
through the reverse route.
Route to Extention monitor:
The voice signal from Door station is sent through another HYB, and interphone cable to Extention monitor.
In Extention monitor, The voice signal from Monitor station is sent through HYB and Sub CPU to the speaker of Extention
monitor.
While the voice from the microphone of Extention monitor reaches the speaker of the Door station through the reverse route.
Command signal route:
The CPU command on Door station is modulated to ASK signal and sent to the Monitor station.This ASK signal is
demodulated in Monitor station to pass to the CPU, and vice versa. (2-way communication)
Route to Extention monitor:
The Main CPU command of Monitor station is modulated to ASK signal and sent to Extention monitor.
This ASK signal is demodulated in Extention monitor to pass to Main CPU, and vice versa. (2-way communication)
Fig. 4.1. Video intercom system block diagram
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