Zeadio Modular 8 Pin Handheld Remote Speaker Dtmf Keypad Mic Microphone for Icom Radio Ic-f1821 Ic-2000/h Ic-2100h Ic-2200h Ic-f320 Ic-f420 Ic-fr4100 Etc. DTMF(Dual Tone Multi Frequency) function will open the radio's squelch only when it receives a DTMF code that matches one pre-programmed into your receiver. Each tranceiver is normally programmed with a unique code. With RJ 45 8-Pin modular connector Built-in PTT and microphone is very handy Talk and listen without ever HOLDING your radio/transceiver &lt;b&gt;Sold exclusively by Zeadio&lt;/b&gt;