Practical Asterisk 1.4 and 1.6: From Beginner to Expert

18. Busy Lamp Field, Hints, Pickup

Philipp KempgenStephen Bosch

The Busy Lamp Field, or BLF, is a common feature of many modern telephone systems. The BLF can be colored LED lamps or LCD indicators that allow a user to monitor the status of other users on the system, almost always next to a button that performs an operation on the monitored station depending on the status of the indicator. Although it is most frequently seen at reception switchboards, it can also be found on regular desktop sets.

The indicator tells the operator the status of the line. A line can have many states:

• Ringing

• Busy or “in use” (which usually includes active “Do not disturb” states)

• On hold

• Available

The states can be indicated with LED lights (which may change ...