Is often met in business practice, during calls to organizations at the moment, when the call is transferred to another number or is set on hold, one hears a music in the telephone dynamics.
Gatekeeper is an administrational tool for H.232 multimedia networks. A single unit can control interactions for each zone, which comprises the terminals, MCU's and gateway within the frames of a particular domain. Gatekeeper is an optional element, but when it available, it becomes the central administrative entity.