Handspring Treo 300 - Manual (Page 220)

Section 7
212 Setting Preferences for Your Phone
4. Hold Option and press Return to finish.
To select ring tone settings:
1. Tap the Tone box.
2. Tap the various call tone pick lists and select a ringer sound for each
of the following types of incoming calls:
Known
Caller Plays this sound when you receive a call that matches any number
stored in your Speed Dial or Contacts list. This setting is independent
from the unique ring you can assign to specific numbers in your
Speed Dial list.
Unknown
Caller Plays this sound when you receive a call from a number that does not
match any of the numbers stored in your Speed Dial or Contacts list.
Roaming Plays this sound when you receive a call while roaming outside a PCS
coverage area.
Message Plays this sound when you have a text message.
Voicemail Plays this sound when you have a new voicemail message.
Service Plays this sound for PCS related notifications.