How is over the air access to Internet Radio Linking Project (IRLP) nodes accomplished?
Why IRLP links repeaters and simplex nodes together over the internet, and the node computer listens for commands from users on the radio. Those commands are sent as DTMF touch tones from the microphone keypad, typically a node number to connect and a code such as 73 to disconnect. The node's controller decodes the tones and tells the IRLP software which remote node to call.
Watch out CTCSS tones are sub-audible tones used only to open a repeater's squelch, they carry no digits and cannot select a node number. Internet passwords are used by the node owner at the computer, not by users on the air.
Link over the air with the touch keypad: DTMF dials the node number, just like a telephone.