Yealink SIP-T48G Administrator's Manual page 684

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
3. Select the desired ring tone from the pull-down list of Ring Type.
4. Click Confirm to accept the change.
To select a ring tone for the phone via phone user interface:
1. Press Menu->Settings->Basic Settings->Sound->Ring Tones->Common.
2. Press
3. Press the Save soft key to accept the change or the Back soft key to cancel.
To select a ring tone for the account via phone user interface:
1. Press Menu->Settings->Basic Settings->Sound->Ring Tones.
2. Press
3. Press
If Common is selected, this account will use the ring tone selected for the phone.
4. Press the Save soft key to accept the change or the Back soft key to cancel.
Distinctive ring tones allows certain incoming calls to trigger IP phones to play distinctive
ring tones. The IP phone inspects the INVITE request for an "Alert-Info" header when
receiving an incoming call. If the INVITE request contains an "Alert-Info" header, the IP
phone strips out the URL or keyword parameter and maps it to the appropriate ring
tone.
Note
If the caller already exists in the local directory, the ring tone assigned to the caller
should be preferentially played.
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or to select the desired ring tone.
or to select the desired account and then press the Enter soft key.
or to select the desired ring tone.