Yealink SIP-T48S User Manual page 190

User Guide for the SIP-T48S IP Phone
The phone will send the configured on code or off code depending on your selection when
you enable or disable anonymous call rejection feature on the phone.
Tap the Save soft key to accept the change or
6.
Anonymous call rejection is configurable via web user interface at the path Account->Basic.
If phone B has anonymous call feature enabled and places a call to your IP phone, the call will be
rejected, and the touch screen of the phone B will display the following:
180
to cancel.