The busy lamp field is a function of IP phones that are supported by all Snom phones to display the busy information of the connected devices on other phones.
Depending on the IP PBX (IP PBX system), the extended version BLF & DND is also supported, where pressing the DND button also leads to a red (busy) light on the BLF button.
The fields are either integrated in the telephone or connected to the telephone as an additional module, or both and usually consist of several speed dial keys, each with an associated LED. If one of the stations stored on the speed dialling keys is called, the corresponding LED flashes - if its connection is busy, it lights up continuously.
The keys have different functions depending on the status of the subscriber: If the subscriber is free, he is called when the corresponding speed-dial key is pressed, if the subscriber is being called, the call can be retrieved by pressing the key.
The phone subscribes for the dialog state of the configured extension and receives notifications regarding to the state of the extension. The following dialog states are indicated by distinct LED behavior: