Yealink SIP-T4X Administrator's Manual page 157

Busy Lamp Field (BLF) is used to monitor a specific user for status changes on IP phones.
For example, you can configure a BLF key on a supervisor's phone to monitor the phone
user status (busy or idle). Then when the user places a call, a busy indicator on the
supervisor's phone indicates that the user's phone is in use.
When the monitored user is idle, the supervisor can press the BLF key to dial out the
phone number. When the monitored user receives an incoming call, the supervisor can
press the BLF key to pick up the call directly. When the monitored user is on a call, the
supervisor can press the BLF key to interrupt and set up a conference call.
Visual Alert and Audio Alert for BLF Pickup
Visual alert and audio alert for BLF pickup allow the supervisor's phone to play an alert
tone and display a visual prompt (e.g., ―6001<-6002‖, 6001 is the monitored extension
and receives an incoming call from 6002) when the monitored user receives an
incoming call. In addition to the BLF key, visual alert for BLF pickup enables the
supervisors to pick up the monitored user's incoming call by pressing the Pickup soft key.
The directed call pickup code must be configured in advance. For more information on
how to configure the directed call pickup code for the Pickup soft key, refer to
Call Pickup on page 105.
BLF LED Mode
BLF LED mode provides four kinds of definition for the BLF key LED status. As there is no
hard line key on SIP-T48G IP phones, BLF LED mode is only applicable to
SIP-T46G/T42G/T41P IP phones. BLF LED mode configuration is also applicable to the
expansion module EXP40 connected to SIP-T48G/T46G IP phones. The following table
lists the LED statuses of the BLF key when BLF LED Mode is set to 0, 1, 2 or 3 respectively.
The default value of BLF LED mode is 0.
Line Key/Expansion Module Key LED (configured as a BLF key and BLF LED Mode is set
to 0)
LED Status
Solid green
Fast flashing red (200ms)
Solid red
Slow flashing red (1s)
Off
Description
The monitored user is idle.
The monitored user receives an incoming call.
The monitored user is dialing.
The monitored user is talking.
The call is parked against the monitored user's phone
number.
The monitored user's conversation is placed on hold.
The monitored user does not exist.
Configuring Advanced Features
Directed
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