Recommendation ITU-T H.450.5 describes the procedures and signalling protocol scenarios for the Call Park and Call Pickup supplementary services in ITU-T H.323 systems.The Call Park supplementary service (SS-PARK) enables User A (the parking user) to place an existing call with User B (the parked user) in a parking position.The call can later be picked up by retrieving the parked party from either the same terminal where the park took place or from another terminal.The Call Pickup supplementary service (SS-PICKUP) enables the picking-up user to pick up either a parked call or an alerting call.Upon successful invocation of SS-PICKUP, the picking-up user is connected with the parked user or with the calling user,depending on selection.