anchor.diff:  To shut down the syncing, just call `sync-to-external-clock` with no
   sync source:
   
  -code,clojure----------------------------- code,clojure
  +[source,clojure]
  +----
   (show/sync-to-external-clock)
   (show/sync-status)
   ; -> {:type :manual}
  ------------------------------
  -
  -[[syncing-to-pro-dj-link]]
  -Syncing to Pro DJ Link
  -~~~~~~~~~~~~~~~~~~~~~~
  +----
  +
  +== Syncing to Pro DJ Link
   
   If you are working with Pioneer club gear, such as the Nexus line of
   CDJs and mixers, you can use Pro DJ Link to sync much more precisely.
  
positive.code: being played). Like with MIDI sync, you can give a unique substring of
  the device name in the sync call:
  
  code,clojure-------------------------------------------------
  code,clojure
  (show/sync-to-external-clock
    (afterglow.dj-link/sync-to-dj-link "DJM-2000"))
  -------------------------------------------------
  
  As with MIDI, you can check on the sync status:
  
  code,clojure---------------------------------------------------------------
  code,clojure
  (show/sync-status)
  ; -> {:type :dj-link, :status "Running, 5 beats received."}
  ; -> {:type :dj-link,
  ;     :status "Network problems? No DJ Link packets received."}
  ---------------------------------------------------------------
  
  _______________________________________________________________________________________________________________________________________________________________________________________________________________________
  If you are not getting any packets, you will need to put on your network
  troubleshooting hat, and figure out why UDP broadcast packets to port
  50001 from the mixer are not making it to the machine running Afterglow.
  _______________________________________________________________________________________________________________________________________________________________________________________________________________________
  
  [[checking-your-sync]]
  Checking your Sync
  ~~~~~~~~~~~~~~~~~~
  
  An easy way to see how well your show is syncing the beat is to use the
  metronome-cue, which flashes a bright pink pulse on the down beat, and a
  less bright yellow pulse on all other beats of the show metronome. To
  set that up:
  
  code,clojure------------------------------------------------------------
  code,clojure
  (require 'afterglow.effects.fun)
  (show/add-effect! :color
    (afterglow.effects.fun/metronome-cue (show/all-fixtures)))
  ------------------------------------------------------------
  
  Then you can reset the metronome by hitting Return on the following
  command, right on the down beat of a track playing through your
  synchronized gear, and watch how Afterglow tracks tempo changes made by
  the DJ from then on:
  
negative.code: 
  [source,clojure]
  ----
  (show/add-effect! :color (global-color-cue
    (params/build-color-param :s 100 :l 50 :h :knob-1)))
  ----
  