NEC FP1355 Service Manual page 60

[Composite synchronizing signal] (Composite Sync)
The composite synchronizing signal which has been input from SINGAL-A is input from pin 13 of D-SUB
connector J215 to pin 15 of analog switch IC216. While, the composite synchronizing signal which has
been input from SINGAL-B is input from pin 13 of D-SUB connector J216 to pin 7 of analog switch IC216.
(Refer to A point.)
Analog switch IC216 selects a signal (2-input change over) when SIGNAL-A and SIGNAL-B are simulta-
neously input, as well as the separate synchronizing signal.
As for the method of selecting a signal, like the separate synchronizing signal, according to SELECT
signal of pin 53 of microcomputer IC101, the input signal of SIGNAL-A is selected when pin 13 (SELECE
SW) of analog switch IC216 is HIGH, and the input signal SIGNAL-B is selected (refer to B point) when it
is LOW. Either signal is output from pin 19 of analog switch IC200. (Refer to C point.)
The composite synchronizing signal output from analog switch IC216 is supplied to pin 30 of microcom-
puter IC101 on PWB-MAIN via the flat cable, and its synchronization is separated at microcomputer
IC101.
Figure 27 2-input change over circuit and composite synchronizing signal
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