Pickup() — Answers a ringing call from another phone
Picks up any ringing channel that is ringing the specified
extension. If multiple extensions are
specified, Pickup() will retrieve the
first matching call found. If no context is
specified, the current context will be used.
There is also a special context name of
PICKUPMARK. If specified, Pickup will find the first ringing channel
with the channel variable PICKUPMARK
set, with a value corresponding to the value of
extension.