The service allows you finding out who has called you, when the telephone line was busy, switched off or was outside the zone of coverage. By doing so, it ensures that an important call will not be missed.
Cisco 6921 is inexpensive business class IP phone model supporting video connection (Cisco UC Phone 6921, Standard Handset).
Cisco 6921 IP phone supports up to 2 lines has full-duplex loudspeaker, supports call holding on each line, hold, transfer, conference keys, tricolor indication of line condition, functional keys for simplified use of IP phone functions.