Standard Horizon HX870 Owner's Manual page 24

VOL− key
Press to decrease the speaker audio volume level.
16/S key
Pressing this key immediately recalls channel 16 from any channel
location. Holding down this key recalls the SUB channel (The default
setting is channel 9). Pressing this key again reverts to the previous
selected working channel.
CLR key
Press this key to cancel a menu selection and/or keypad entry.

MIC/SP jack (Top side)
The jack accepts the optional MH-73
MH-57 Mini Speaker/Microphone, VC-24 VOX Headset, SSM-10
A4B
Submersible Speaker/Microphone, or SSM-55A Earpiece/Microphone.
When this jack is used, the internal speaker and microphone are disabled.

DATA jack (Right side)
Use the USB mini type B jack to output the NMEA data, configure the
transceiver settings and download the GPS logger data.
DISTRESS key (Right side)

Used to send a DSC Distress Call. To send the distress call, refer to section
"9.3.1 Transmitting a DSC Distress Call".

Soft keys
The 3 programmable soft keys can be customized by the Setup Menu
mode described in section "12.7 SOFT KEYS". When one of the soft keys
is pressed briefly, the functions will appear above each key on the display.
Strobe light indicator
When the Emergency feature is activated, this indicator blinks the interna-
tionally-recognized Morse Code "S.O.S" message.
When the Water Hazard feature is activated, this indicator illuminates if the
transceiver is submerged.
Speaker
The internal speaker is located here.
Battery pack lock (Bottom side)
Turn the Battery Pack Lock to the "UNLOCK" position for battery removal.
Page 24
Submersible Speaker/Microphone,
A4B
HX870