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Chapter 3: USD Hardware and Software Overview 19
8. Positional Reference LEDs
Yellow LEDs display the active positional
reference.
In Auto Switch LTC/VITC mode, both the
LTC and VITC LEDs light while the USD
determines which source it will use. Either
the LTC or the VITC LED will remain lit to
indicate the chosen positional reference.
9. Frame Rate Switch
Selects the time code frame rate and format
(drop-frame or non drop-frame). The active
choice is displayed by the Frame Rate LEDs.
10. Frame Rate LEDs
Display the current USD frame rate.
Frame Rates
30, 29.97, 25, or 24 fps are in-
dicated by four green LEDs
Drop/Non-drop
Format is indicated by a
single orange LED labelled DF (a lit DF LED
indicates drop frame, unlit indicated non-
drop frame).
11. Status LEDs
Show the current state of the USD in rela-
tion to clock references. Indicators include:
Locked
This red LED lights solid when the
USD is locked to the selected clock refer-
ence. LOCKED flashes if the selected clock
reference source is missing or out of lock-
able frequency range.
Speed Cal (Speed Calibration) This yellow
LED indicates when all output clocks are at
a frequency that corresponds with the cho-
sen sample rate. Speed Cal flashes when-
ever there is a mismatch between the cho-
sen sample rate and the actual output
sample rate.
For example, if the Clock Reference is set to
LTC, and being fed by LTC from an analog
tape that is running somewhat off-speed,
this indicator will flash quickly (if too fast)
or slowly (if too slow). The Speed Calibra-
tion LED will be lit steadily only if the out-
put clock (remember, USD is generating an
output clock from incoming LTC) is within
±0.025% (250 parts per million) of the cho-
sen sample rate. If the speed is greater than
+0.025%, the indicator will flash quickly; if
the speed is less than –0.025%, the indica-
tor will flash slowly.
Relatively new professional ATRs should be
able to play back with a speed deviation of
less than –0.025%. Some ATRs, even when
calibrated properly, may not run accurately
enough to allow the Speed Calibration to
remain lit without flashing.
The Speed Calibration LED compares ac-
tual output sample rate to desired sample
rate. This LED does not reflect the speed of
motion of the chosen Positional Reference.
However, it would bear a relationship to
the Positional Reference if both Positional
Reference and Clock Reference were set to
LTC.
Remote Mode
This green LED lights when
the USD is set to Remote-Only /Front Panel
Lockout Mode. For more information see
the section “About Remote-Only Mode” on
page 29.