Transmit Timeout Timer (Tot); Simplex/Duplex Channel Use; International, Canada, And Usa Mode; Backlight Adjustment - Furuno FM-4721 Operator's Manual

2. OPERATION
2.4

Transmit Timeout Timer (TOT)

When the PTT switch on the microphone is pressed continuously, transmit time is lim-
ited to five minutes. This limits unintentional transmissions due to a stuck PTT switch.
About 10 seconds before automatic transmitter shutdown, a warning beep sounds
from the speaker(s). The transceiver automatically goes to the RX mode, even if the
PTT switch is continually held down. To transmit again, the PTT switch must first be
released and then pressed again.
CAUTION: The heatsink can get hot enough to cause fire or burn injury when the TX
to RX ration goes lower than 1:9.
2.5

Simplex/Duplex Channel Use

Refer to the VHF Marine Channel Chart in the Appendix for instructions on use of sim-
plex and duplex channels.
Note: All channels are factory-programmed in accordance with FCC (USA), Industry
Canada (Canada), and International regulations. Mode of operation cannot be altered
from simplex to duplex or vice-versa.
2.6

International, Canada, and USA Mode

To change the channel Group call from International to Canada or USA:
1. Press and hold down the CALL/MENU key until the [Setup Menu] appears.
2. Rotate the CH knob to select [CH Function Setup] then
press the [SELECT] soft key.
3. Rotate the CH knob to select [CH Group] then press
the [SELECT] soft key.
4. Rotate the CH knob to select a channel Group [USA],
[INTL], or [CAN (CANADA)] then press the [ENT] soft key to store the selected
setting.
Note: When in INTL channel group, inland waterways channel group can be se-
lected from the ATIS menu by switching ATIS to ON. See section 6.2.
5. Press the [QUIT] soft key several times to return to radio operation.
2.7

Backlight Adjustment

Adjust the display illumination for viewing in sunlight or darkness.
1. Press the FUNC key followed by the 4/DIM key to show the [Dimmer] menu.
2. Rotate the CH knob to select the desired level. When
[OFF] is selected, the backlight is turned off.
3. Press the [ENT] soft key to store the selected level,
and return to radio operation.
2-6
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