BLF stands for Busy Lamp Field.

Typically this is a light, or LED light with buttons, on an IP phone that indicates whether another extension or phone is available, ringing or busy. This is a useful feature for busy office environments, remote workers or receptionists who need to swiftly see when colleagues may be available on the phone, without the need to physically visit their desk.

Our VoIP service fully supports this feature on BLF-enabled IP phones as standard. Some BLF-enabled devices such as some Grandstream or Snom IP phones can also allow easy-pickup of calls to colleagues by pressing BLF buttons when new calls come in. Typically BLF functionality needs to first be turned on directly via the IP phone. This is often carried out via the web interface specific to that phone.