Furuno CSH-8L - Manual (Page 48)

3. ADVANCED SONAR OPERATION
3-12
3.8.4 Confirming function key program
You may confirm function key program as below.
1. Press the [MENU] key to open the menu.
2. Use the [RANGE] control to choose [MENU MODE].
3. Use the [GAIN] control to choose SONAR.
4. Use the [RANGE] control to choose ASSIGN MENU. The current programs
are shown at the top of the menu
F1 F1 KEY
F2 F2 KEY
F3 TVG NEAR
F4 TVG FAR
Function key assignment confirmation screen
5. Press the [MENU] key to close the menu.