Yealink SIP-T48G - Manual (Page 157)

Troubleshooting
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authentication if the server requires. Display name is the caller ID that will be displayed
on the callee’s touch screen. Server configuration may override the local configuration.
Why does the phone play a tone when there is a call on hold? How to disable it?
When there is a call on hold, the phone will play a hold tone every 30 seconds. Call hold
tone is enabled by default. Call hold tone and the interval of playing a hold tone are
configurable via web user interface only.
To configure call hold tone and call hold tone delay via web user interface:
1. Click on Features->General Information.
2. Select the desired value from the pull-down list of Play Hold Tone.
3. Enter the desired time in the Play Hold Tone Delay field.
4. Click Confirm to accept the change.
Why does the wallpaper has bad display？
Do one of the following:

Check that the custom image is clear.

Check that the file format of the custom image for the wallpaper is *.jpg, *.png or
*.bmp.

Check that the custom image is not too large or small. The phone will adjust the
image with the short side to display.

Check that the picture resolution of the wallpaper. The wallpaper resolution of the
SIP-T48G IP phone is 800*480 pixels.