Although SIP protocol (RFC3261) was not providing the semantics to support the Busy Lamp Field (BLF) there’s a way around...

Busy Lamp Field (BLF) feature allows an end user, such as attendant, to monitor the hook status of a list...

Grandstream GXP21XX and GXP17XX IP phones have introduced a new VPK (“Virtual Multi-Purpose Keys”) feature to add more flexibility and...