*Question T8C06:
How is over the air access to IRLP nodes accomplished?*  

*Correct Answer is  B: By using DTMF signals*  

### AI Response: (may contain errors)  

To access IRLP (Internet Radio Linking Project) nodes over the air, the correct method is to use DTMF (Dual-Tone Multi-Frequency) signals.

### Explanation of the Correct Answer:
- **Correct Answer: B: By using DTMF signals**
  - DTMF signals are used to send commands to the IRLP node. When you transmit a DTMF tone, it corresponds to a specific command or function, such as connecting to a particular node or disconnecting from a link. This is the standard method for accessing IRLP nodes.

### Explanation of Incorrect Answers:
- **A: By obtaining a password that is sent via voice to the node**
  - This is incorrect because IRLP does not use voice passwords for access. Instead, it relies on DTMF tones to perform functions like connecting to nodes.

- **C: By entering the proper internet password**
  - This option is incorrect as IRLP nodes are accessed over radio frequencies, not through internet passwords. The connection is made using radio equipment and DTMF tones, not through internet authentication.

- **D: By using CTCSS tone codes**
  - CTCSS (Continuous Tone-Coded Squelch System) is used for squelching and preventing unwanted transmissions on a frequency, but it does not provide access to IRLP nodes. CTCSS tones are not used for command signaling like DTMF.

### Summary:
- **DTMF** is the correct method for accessing IRLP nodes, as it allows users to send specific commands over the air.
- Other methods mentioned (voice passwords, internet passwords, CTCSS) do not apply to the IRLP access process.

This understanding is crucial for the Extra Class exam, as it highlights the specific technologies and methods used in amateur radio operations.