Learning Centre
Frequently Asked Questions are broken down into the following 4 main categories:
Cabling
| Question |
Answer |
| What kind of cable should I use with
NVT devices? |
Use Unshielded Twisted Pair, such as CAT5 (or better) or
telephone cable; part CW1308. 24AWG or
thicker, stranded or solid versions. |
| Can shielded twisted pair cable be used? |
Some customers have successfully used
shielded cable up to a few hundred feet.
However NVT does not recommend it as the
transmission distance will be reduced. Using a
multi-pair cable (ten, or more pairs) with an
overall shield is OK. |
| Can the cable run have splices? |
Yes. NVT recommends designing CCTV systems
in much the same way as telephone/data
systems. You can splice the cable, by using a
range of 4 to 100 pair Krone boxes to make
connections. Video has been sent through a
dozen of these connections without
significant degradation. |
| Can Category 6 cable be used? |
Yes. Unshielded Twisted Pair cable, Category 2,
telephone or better, can be used with NVT. |
| Can un-twisted cable be used? |
Some customers have successfully used untwisted
cable. NVT does not recommend it due
to its interference susceptibility. |
| How can I send video from one camera to
more than one monitor using NVT? |
There are a few ways to accomplish this.
One is to connect your video source to a
distribution amplifier. This provides multiple
video outputs for each input. Connect a
transmitter and receiver to each cable run
leading back to each monitor. Another
method is to send the video signal to the first
monitor using a pair of transceivers.
Then loop out of that monitor and use another
pair of transceivers to continue on to the
next monitor. Alternatively you could utilise one of NVT's distribution-amplifier hubs |
General
| Question |
Answer |
| Where would I use the NV-214A-M? |
The NV-214A-M transmitter is designed to
work with any camera. Simply plug the BNC
onto the output of the camera and wire a pair
into the screw terminals. |
| Are NVT transceivers rack mountable? |
Yes. The NV-RM8/10 rack panel will hold up to
ten NV-208A-M, two NV-413A/NV-452R or, ten NV-653T/NV-652R. NVT multi-channel
hubs are also rack-mountable and include the
necessary hardware. |
| Will RF interfere with the video when
using NVT devices? |
No. The NVT signal is highly immune to
interference. NVT signals are sent differentially.
That is, the equipment is only concerned with
the voltage difference between the two
conductors. RF or other fields will still couple into the conductors, but will do so in each
conductor equally. This Common-Mode signal
is ignored by the NVT equipment, which has a
60 dB Common-Mode Rejection Ratio (CMRR). |
| What is the warranty on NVT products? |
All NVT products, including active receivers,
carry a full "Lifetime Warranty" -
demonstrating NVT's confidence in equipment
performance and long-term reliability. |
| Can NVT help me with my design? |
Yes. NVT offer a comprehensive system design
service. This facility offers system drawings
and specification documentation free of
charge, available by contacting the NVT
Technical Support team. |
| What if I need field support, can NVT
help me? |
Yes. NVT will support "on-site" design and
surveys, and also helps with any technical
issues whenever necessary. |
| Where can I purchase NVT products? |
Contact the NVT Sales Department for details
of approved distribution outlets. |
Supported Signals
| Question |
Answer |
| Do NVT transceivers support "up the coax"
pan/tilt/zoom controls? |
Yes. When using passive transceivers to
transmit and receive, "up the coax" control
signals can be sent with the video up to
300 metres. |
| Can NVT devices transmit VGA? |
Yes. The NTSC or PAL output of a VGA or SVGA
scan converter can be transmitted using NVT. |
| Can I transmit more than one video signal
in a multi-pair cable? |
Yes. One of the benefits of using NVT
transceivers is interference rejection. NVT
video signals can reside in the same cable
bundle as multiple video signals, Ethernet,
24VAC, RS-422, RS-485, etc. |
| Can video signals be sent in opposite
directions within the same cable? |
Yes, however, due to near end crosstalk, there
are distance limitations. When using telephone
cable, do not send video in opposite directions
within the same cable more than 300 metres.
With CAT5 (or better), do not send bi-directional video
more than 600 metres. |
| Do NVT transceivers support broadband
RF/VHF/UHF? |
No. Use demodulators and modulators to
convert to baseband composite video. |
| Can I transmit satellite or cable TV using
NVT transceivers? |
No. NVT transceivers do not support the wide
bandwidth cable TV signal. However, a single
channel can be sent if a demodulator and
modulator are used. |
| Can I transmit a multiplexed signal on
unshielded twisted pair? |
Yes, in the same way as you would use a coax
cable, with NVT allow for a pair of transceivers
per output. |
| Can NVT transmit RS-422 or
RS-485 signals? |
RS-422 or RS-485 signals are hard-cabled
between the P/T/Z equipment and are not
transmitted or received by NVT transceivers.
The data signal may be sent on a spare pair
within the same cable as the video signal. |
Troubleshooting
| Question |
Answer |
| When using the NV-652R, the green
"signal present" light is lit, but the blue
"power" light goes out and there is no
video. What does this mean? |
Most often, this indicates that the supply
powering the NV-652R is not floating.
Use a supply with an isolated output. |
| When transmitting video between passive
NVT transceivers, the video is wavy and
there is a dark bar that rolls upward on the
monitor. Why? |
This is the result of a ground loop. Use an
active receiver (which has built-in ground
lifting), or 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. |
| Why is the green light flickering on the
active receiver? |
This usually indicates a poor connection along
the cable path. |
| Why is there a double image in my video? |
Faint shadows of the original signal shifting to
the right, or "Ghosting" occurs when there is
an impedance mismatch along the cable. Verify
that the monitor is terminated with 75Ω (not in
loop-through). Check for, and remove any
bridge-taps (another cable pair connected to
the cable run). |
Why does my video look like a scrambled
Cable TV signal? |
This typically indicates reversed polarity
of the cable. |
