How is over the air access to IRLP nodes accomplished?

Over the air access to IRLP (Internet Radio Linking Project) nodes is controlled using DTMF (Dual Tone Multi-Frequency) signals. These are the standard keypad tones found on most amateur radio transceivers, similar to a traditional telephone keypad. When an operator wants to link their local repeater to a distant IRLP node, they transmit a specific numerical sequence using their radio's keypad. The local node translates these DTMF tones into commands that open a VoIP connection across the internet. Distractors like CTCSS are incorrect because they are used to open a repeater's squelch, not to dial or route internet node connections.