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Directed Call Pickup

  Pickup(extension[@context][&extension2@context...]): This application can pickup any ringing channel
that is calling the specified extension. If no context is specified, the current
context will be used. If you use the special string "PICKUPMARK" for the context parameter, for example
10@PICKUPMARK, this application tries to find a channel which has defined a channel variable with the same content
as "extension".