ART Pro Audio SyncGen - Word-Clock Generator - Manual (Page 5)

If the Termination LED is RED, then there is an output-loading problem, and the output may be too
low to function. Try removing the 75 Ohm terminator if you added one onto this output. If that is NOT
the cause, then the output may be shorted. (A defective or improperly connected cable could cause
this.)
If an output is unterminated or unused, the LED will not light.
The SyncGen uses discrete 75 Ohm output drivers that adapt to the output load. Each output is
protected from shorts and over-voltage due to accidental incorrect termination.
Termination and why it is needed
A terminator is simply a resistor connected between the signal and ground at the end of a cable.
Termination reduces the reflections from the undriven end of a cable. These reflections can skew the
timing of the waveform leading to timing errors. The longer the cable run, the worse the errors are
that can be created.
A green termination LED will indicate that a SyncGen output is correctly terminated.
If you have too many terminators or a cable short, the LED will light red. This typically happens when
you have a device with internal termination and you add a 75 Ohm terminator to the cable as well.
An easy way to check for internal termination is to connect to the digital audio unit that you are unsure
of, and check the termination LED. If it lights green, this device has internal termination.
The SyncGen can also double as a handy BNC wordclock cable tester. First connect a cable; the
termination LEDS should remain unlit indicating no short circuit. Next connect a 75 Ohm terminator
using a BNC “T” adaptor. The termination LED should light green indicating a good connection.
S/PDIF outputs
Two coaxial S/PDIF outputs are provided to allow synchronization of digital audio devices that lack
BNC wordclock inputs. Devices like the Digidesign Digi 002 have coax S/PDIF inputs that can be
selected as the source for timing reference. Use this input with the ART SyncGen to tie the timing of
this device in with the rest of your system. The SyncGen’s S/PDIF output has all audio bits set to zero
“digital black”, providing a locking source for these applications.
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