Humminbird DC 25 - Manual (Page 6)

VOLUME ON/OFF turns power to the radio on and off, and controls the volume of both the built-in
speaker and any auxiliary speaker connected to the radio. When power is first turned on, the
radio is automatically set to Channel 16 (emergency and calling) in the USA frequency band.
SQUELCH eliminates background noise when the radio is not receiving a signal and controls the
sensitivity of the scan function.
CHANNEL selects the channel to use for transmission and reception in the current frequency
band (selected with the USA/INT and WX buttons). Turning the knob to the right advances
through the channels in ascending order, and turning it to the left selects channels in descending
order. Note that some channels have a specific purpose; be sure to see the “Table of Marine
Channels” that appears later in this manual.
SCAN scans all channels for signals in the selected frequency band. Pressing SCAN causes the
radio to begin scanning from the lowest channel, and to lock in on the first channel for which a
signal is detected. When a signal is no longer present on that channel, scanning resumes. There
are several ways to channel scan: Press the scan BUTTON again, press the microphone button
once, or turn the CHANNEL knob. Scanning is also cancelled if you press the CH 16 button.
DUAL enables the “dual watch” function, which lets you monitor Channel 16 while receiving on
any other channel. The radio switches immediately to Channel 16 of the last-selected frequency
band (USA/INT) when a call is detected, then switches back when the Channel 16 call is
completed. To cancel dual watch, press the DUAL button again.