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However, some film equipment works in the opposite manner, which is why the Sync X Bi-Phase Tach Wiring setting in the Peripherals
dialog lets you make the appropriate selection (Fwd = A leads B, or Fwd = B leads A).
Calculating the direction of a Tach signal is slightly different. Tach uses two signals: the “A” signal is a square wave that provides clock
information; the “B” signal is in a steady state (high or low) that indicates the direction. However, not all Tach-generating equipment
uses the B signal in the same way. The Sync X
Bi-Phase Tach Wiring setting in the Peripherals dialog lets you select the appropriate
method (Tach: Fwd = B is Low, or Tach: Fwd = B is High).
Pilot Tone
Sync X can resolve to an external Pilot Tone signal for synchronizing to (or transferring audio from) certain types of open-reel audio
tape recorders. Pilot Tone is a sine wave reference signal running at the “line frequency” or “mains frequency,” meaning the same fre-
quency transmitted by the AC line voltage from the local power utility.
Pilot Tone is used on location film shoots to establish a common synchronization reference between a film or video camera with a por-
table 1/4-inch analog ATR (such as those made by Nagra or Stellavox). On location, Pilot Tone is derived by clock referencing the cam-
era to the local AC line frequency (which is 60 Hz or 50 Hz depending on the country of origin), and this same frequency is then recorded
on one of the tracks of the ATR. The result is that both the camera and the ATR will maintain synchronization when played back. Some
1/4-inch machines have a center track for timecode or Pilot Tone.
Note that Pilot Tone contains no positional reference information.
MTC (MIDI Time Code)
MTC (MIDI Time Code) embeds the same timing information as standard SMPTE timecode as a series of MIDI messages every quar-
ter-frame. MTC messages are transmitted in a sequence of eight messages, transmitting a timecode value every two frames. Sync X
transmits one full sequence of MTC Quarter-Frame Messages every 200 milliseconds when MTC Idle is enabled.
Unlike standard SMPTE timecode, MTC quarter-frame and full-frame messages carry a two-bit flag value that identifies the rate of the
timecode, specifying it as one of the following:
• 24 frame/s (standard rate for film work)
• 25 frame/s (standard rate for PAL video)
• 29.97 frame/s (audio and video—MIDI spec assumes drop-frame, but Sync X uses this for both drop-frame and non-drop-frame)
• 30 frame/s (audio and video—MIDI spec assumes drop-frame, but Sync X uses this for both drop-frame and non-drop-frame)
Other MIDI devices can synchronize their timecode address using the Sync X MTC output.
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