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3
Wiring Notes
Wire — What to DO
1.
DO
use point-to-point Unshielded Twisted Pair wire, gauge 24 or thicker, stranded
or solid, Category 2, 3, 4, or 5.
2. The video signal may co-exist in the same wire bundle as other video, telephone,
data, control signals, or low-voltage power. It is also OK to run NVT video signals in
or near electromagnetic fields
(in accordance with National Electrical Code, local,
or other local safety requirements)
.
3.
DO
measure the wire distance. Use only transceivers that are designed for that
distance.
4.
DO
make sure the pair of wires carrying the video signal is sent as a twisted pair
(e.g. the blue-white/white-blue wires twisted together as a pair)
, not a “split-
pair”
(e.g. blue-white conductor, part of one pair/orange-white conductor, part
of another pair)
.
Wire — What NOT to DO
1.
DO NOT USE SHIELDED TWISTED PAIR WIRE
. It will severely degrade the
distance performance. Short runs may be used with some signal degradation
(for
example elevator traveler cables)
. Multi-pair wire with an overall shield is OK.
2.
DO NOT USE UN-TWISTED WIRE
. It will reduce the NVT product’s inherent
interference immunity.
3.
DO NOT
allow your installation to have “bridge-taps”, loading coils, talk-battery,
or MOV type protectors. Bridge-taps are where a twisted pair is connected to two
twisted pairs
(such as an extension phone at home)
. Bridge-taps cause reflections
as the signal propagates, resulting in “ghosts” in the video image, and are to be
avoided.
4. If the phone company is providing the cable runs between buildings, make sure
it’s “dry copper” i.e. it should have none of the following: dial-tone, 48 volts, loading
coils, bridge-taps, switching, or long paths to the phone company’s central office and
back.
5. Due to near-end crosstalk,
DO NOT
send a transmit and a receive signal in the
same wire bundle. Exceptions: Less than 1,000 ft (300m), or Category 5 cable, up to
2,000 ft (600m) are OK.
6.
DO NOT
send “Up-the-Coax” Pan/Tilt/Zoom signals through active
(amplified)
NVT transceivers.
Measure your wire distance
Note:
All NVT quoted distance specifications include any coax in the run. It is
recommended that the wire distance be measured to ensure that the capability of the
NVT product is correct.
Wire resistance may be measured with an ohm-meter by shorting the two conductors
together at the far end, and measuring the loop-resistance out and back. Compare
your readings with the charts in the next column.
7. For safety, never put NVT signals in the same conduit as high-voltage
wiring.
8.
WARNING
— to reduce a risk of fire or electrical shock, do not expose
this product to rain or moisture.
