Envision Peripherals NV3128 Configuring the Reference Input, Reference Input Ground Obsolete

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

NV3128 RS-422A Machine-Control Routing Switch 2-13