Camera
Monitor
Bridge Tap
NV-213
A
NV-213
A
- 10 -
If the voltage is greater than 1/2 volt, use an amplified receiver,
such as the NV-652R, NV-862R, or NV-1662R.
Alternately, remove the ground at one end (usually at the camera
end). Be sure that floating the camera conforms to local/regional
and National Electrical Codes.
NO GREEN LIGHT, NO VIDEO
The NV-652R, NV-862R or NV-1662R series receiver/hub is not
detecting a video signal. There is an open or shorted connection.
Use a multimeter to locate the fault.
GHOSTS
Faint shadows of the original signal shifted to the right. This is
caused by an impedance mismatch along the wire. Verify that the
monitor is terminated with 75 (not in “loop-through”.) Check that all
wire is
unshielded
twisted pair. The high-frequency wire impedance
should be 100. Check for bridge-taps (see below) either by inspecting
wiring closet connections, or, if available, using a “Time-Domain
Reflectometer” (T.D.R.), sometimes called a “cable tester”.
If the faint shadows are not copies of the original picture, but from the
picture of some other camera, check for crosstalk:
Is any portion of the wire un-twisted?
Are the signals from two cameras split between two pairs?
Is there a short between a conductor of one signal and a conductor
of another?
4. Check for crosstalk from a second video path. Disconnect all other
video sources. If the problem goes away, check for a split-pair or
un-twisted wire.
FAINT STRIPES GLIDING UP OR DOWN THE SCREEN
These are caused by crosstalk from a second video path, or with
ground-loops in installations employing passive models at both ends.
1. To identify, disconnect all other video signals temporarily. If the
interference goes away, check the wire to make sure the signal is
traveling through a twisted pair. Is two-way video being sent more
than 1,000 ft (300m) over Category 2 or 3 wire? If so, the send
and receive signals may need to go in separate jacketed cables, or
upgrade to Category 5 wire.
2. Next, check for ground loops. See #3 above.
NO POWER LIGHT ON THE NVT UNIT
Check the blue “power” LED on powered NVT units. If the light is not
on, the receiver is not getting power. Re-check the power source and
connections.
If the green LED is on but the power LED is off, check that the power
supply is floating. Grounding one side of the power input may cause
this condition.
