Envision Peripherals NV3128 - Manual (Page 37)

NV3128 RS-422A Machine-Control Routing Switch 2-13
2.2.7 CONFIGURING THE REFERENCE INPUT
The NV3128 can derive its timing from a Video Reference input, or it
can free run. The reference input is normally a video black burst signal,
but optionally can be an AES/EBU digital audio bitstream.
Both video and audio reference inputs require that their connection
end-points be terminated in the cable’s characteristic impedance to
avoid line reflections. When the NV3128 is the “end of the line” for
either reference signal, the connection should be terminated in 75
ohms (video) or 110 ohms (digital audio). When the reference input
connection is “daisy chained” or looped through the NV3128 and end-
terminated at some other piece of equipment, the NV3128 termination
should be set to a high impedance.
For the newer Universal Control Card, the reference should be
terminated at the looping connector on the back of the frame. For the
older Command Interpreter, jumper J72 selects the reference video
impedance, and jumper J190 selects the AES/EBU reference input
impedance.
IMPEDANCE SELECT (OBSOLETE)
JUMPER FUNCTION 1-2 2-3
J275 Video Ref In 75 ohms High Impedance
J190 AES/EBU Ref In 110 ohms High Impedance
REFERENCE INPUT GROUND (OBSOLETE)
Jumper J298 on the connector interface module selects the AES/EBU
reference input shield termination.
TERMINATED FLOATING
1-2 2-3