CAVERN Network • Audible Signal Tones

CAVERN Network Control, Group Leaders and Volunteer Emergency Radio Network operators (with a GMRS radio+license) can use audible DTMF tones as signals over the network to get attention and indicate various conditions. When these audible tones are heard, it encourages others to be alert for additional information (especially during emergencies).

These tones are sent using the radio’s numeric keypad:

CAVERN’s standard GMRS radio, the BTECH GMRS-V1

NOTE: CAVERN’s Retevis RT-22 FRS radios are NOT able to transmit tones (no keypad).

How to Send Tones

First, set your radio to the CORRECT CHANNEL!

Next, generate the DTMF audible tones (on a BTech GMRS V1 radio) by holding down the upper Transmit Button (on the left side of the radio) and pressing keys as described in the sections above.

 Hold down Transmit       Press “Star“,”Pound“, etc

PRESS quickly on a key for a SHORT tone.
HOLD down a key to send a LONGER tone.
Use the Number keys to send the ‘musical’ signals.


The two basic audible tone signals proposed for the CAVERN network are:

(1) HELLO Signal

Keys                                                  Name                                      
 #                                                     “HELLO

Hold # key down for between two to four seconds (e.g. “two-one-thousand”)
Optionalpay attention‘ signal, used to start meetings, check-ins, etc.

NOTE: This HELLO signal could be used to before other signals. During an ongoing/active Fire incident, a HELLO signal sent late at night before an “everything’s OK for now” update may be shortened to ~1 second. For additional brevity, ‘double-tapping’ a single tone (beep-beep) could be used as a late night hourly-on-the-hour “all’s well” message.

(2) EMERGENCY Alert Signal

Keys                                                  Name                                      
 # * # * # *# *                                “EMERGENCY !

Only sent to Emergency Alert Channel (FRS 9, GMRS 33).
Only sent by Net Control or a Group Leader (with a GMRS radio).
• Alternate “pound” and “star” keys (like an ambulance siren).
• Each keypress is less than one (1) second.
• Pause for one second between pairs.
• Four (4) repetitions of the tone-pairs is sufficient.

NOTE: If you heard this signal, it would mean there is a serious emergency somewhere nearby! After this signal, there would be additional information transmitted over the Main Repeater Channel (FRS 8, GMRS 23), including the incident location. Do more than just listen: you should get ready to move fast in case it’s somewhere near you!

Special Audible SignalsA VERN Proposal for Network Control / Group Leaders

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