Longitudinal Time Code (Ltc) - Alesis AI-2 Reference Manual

29.97 Hz/30 and if on, to 25 Hz/25. This however automatically
switches if a different code type is detected at the reader input.
The digital audio sample rate at the AI-2's word clock outputs is
always set to the ADAT's standard operating frequency of
48.000 KHz

5.8 LONGITUDINAL TIME CODE (LTC)

The AI-2 has a longitudinal time code generator which is used to
supply the BRC and other external devices with LTC. The AI-2
takes the ADAT time code on tape and converts it to either SMPTE
or EBU time code. The AI-2 time code generator is not intended to
be a generator in the traditional sense but a simulation of a normal
analog tape, time code output. The time code generated is not
ADAT absolute time, as shown on the ADAT front panel, but a
virtual or relative time code, that is ADAT tape time minus the
AI-2 offset.
For example, if the ADAT time is 30 minutes and the offset is minus
1 hour then the AI-2 time code output would be 1 hour, 30 minutes,
calculated as follows:
(00:30:00:00) - (-1:00:00:00) = (01:30:00:00)
From this calculation, it should be noted that the negative one hour
offset gives a positive time code output. If the offset is positive then
the calculation would be as follows:
(00:30:00:00) - (1:00:00:00) = (23:30:00:00)
In this example the time code calculation wraps around the 24 hour
boundary and the time code output will be 23 hours and 30 minutes.
The AI-2 time code output can be selected to generate when the
ADAT is in play only or when it is in play and wind modes. The
code in fast forward and rewind is generated in play speed bursts,
with frame numbers dropped out so that it keeps up with the tape
position. The AI-2 also generates continuous VITC style time code
when the transport is in stop. The generator mode and still options
are selectable in the reference setup menu.
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