Furuno FS-1570 Service Manual page 213

To measure tone frequency;
1. With RT display, press [SETUP] to show Setup menu.
2. Move the cursor over SYSTEM and press [ENT]. The System setup menu protected
is displayed.
3. Enter the password, xxxxxx to unlock the system menu.
4. Move the cursor over TONE and press [ENT]. Tone Tx test menu appears.
5. Move the cursor over TONE and press [ENT].
6. Select either MARK or SPACE, followed by [ENT].
7. Move the cursor over DSP and press [ENT].
8. Select either "DSC" board or "NBDP" board, followed by [ENT]. For example,
select "DSC".
9. Connect the frequency counter to TP4 on the DSC board selected.
10. Move the cursor over TX KEY and press [ENT].
11. Read the frequency on the counter.
Fig.7.2.5 DSP board
7-11
7.2 Frequency
TP4
TONE measurement