Furuno FS-1570 Service Manual page 180

6.1 Self-test
RCVR 2
The test flow is the same as that of "RCVR 1" check.
DSC general frequencies watch receiver (W/R2 board, 05P0734) is tested. When W/R2
board is not installed, RCVR2 line is blank.
The J2B signal, modulated by mark and space tones, is connected to the antenna input
using a stray capacitor. The level is about 70 to 80 dB. DSP board (Modem) detects the
tone signal when W/R2 board is normal. When W/R2 is installed, INST signal of "L"
level is sent to T-CPU from J2-#12 on W/R2. Thus, T-CPU knows the presence of
W/R2. See Fig.6.1.1 for test signal flow.
TRX
TX/RX board is tested. The J2B, 18 MHz signal, modulated by mark and space tones, is
coupled to the antenna input line by a capacitor, C201. The level is about 20 to 30 dB.
DSP board detects the tone signal when TX/RX board is normal.
Fig.6.1.2 TRX test signal flow
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