Furuno FS-1570 Service Manual page 196

6.5 TEST function in DSC SETUP menu
TX/RX PCB test
Test mode and the test frequency are set to adjust PLL and to confirm receiver sensitivity.
SYS ADJ CH sets the frequency for PLL adjustment and SEN CHK CH for receiver
sensitivity check. The channel frequency can be changed. 18MHz receiver test signal is
switched on/off by using TEST SIG line.
The frequency on FREQ SWEEP line is set by rotating the knob.
W/R PCB test
This menu is similar to TX/RX PCB test menu. SYN ADJ CH is used to adjust PLL on W/R
board and SEN CHK CH to check the receiver sensitivity of W/R board.
TA TEST
This test is used at type approval.
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