In PoE parlance, the transmitter is known as Power Sourcing
Equipment (PSE). It is capable of supporting conventional ether-
net, PoE, and PoE+, as well as high power devices up to 50
watts. As such, the transmitter can support an IP camera that
employs an ethernet powered P/T/Z/heater/blower.
Unlike conventional PoE, voltage-drop and load current must be
confirmed by the installer. See page 8 and/or use the IP
Distance Calculator at www.nvt.com.
NVT’s Class 2 current limiting ensures safety of the installation
during fault conditions, while delivering higher power with more
efficient allocation amongst loads.
WARNING: For safety,
never use more than two power supplies within a TBus
channel. Never exceed 120 watts within a TBus channel.
Never use more than one 60 watt remote power supply
on each Hub-based TBus channel
.
Although NVT transceivers may be connected to PoE-enabled
switch ports, they do not use PoE power from the switch, rely-
ing instead on their own higher current 56VDC power sources.
Most IP cameras can support multiple video streams using vari-
ous protocols. MJPEG and H.264 are the most common, and
can be transmmitted at various rates using unicast (point-
to-point) or multicast (single source with multiple destinations).
The NV-ET1801 supports aggregate bandwidths up to 150
Mbps, allowing many devices to operate smoothly on one TBus
network. The 150 Mbps bandwidth is dynamically allocated
amongst all devices on the TBus network, so care must be
taken to not exceed the bandwidth capabilities of the transmis-
sion path.
Some protocols, such as TFTP, are particularly ‘chatty’, meaning
they generate a lot of acknowledgements that can easily clog a
network. NVT recommends simpler protocols for video trans-
mission, such as RTP over UDP.
PoE CONSIDERATIONS
STREAMING PROTOCOL CONSIDERATIONS
BUS ARCHITECTURE
Page 6 of 15
Network Video Technologies
(+1) 650.462.8100 • +44 (0) 208 977-6614
nvt.com • [email protected]
NETWORKING CONSIDERATIONS
Unlike point-to-point devices that require one device at each
end of every cable, TBus transceivers communicate using a
bus-architecture.
This means that multiple remote camera-end transmitters may
be connected together to one receiver at the control-room.
Wire may be star topology, daisy-chained, or any combination.
TBus supports virtually any type of wire, including coax, UTP,
STP, even un-twisted wire. And different wire types can be
concatenated together, as needed.
Coax cables are connected together using BNC splitters,
available from NVT, or elsewhere. If you purchase BNC “T”
connectors from another supplier, please purchase high quality
connectors. Low cost connectors have been found to have
intermittent shield con-
nections.
UTP and STP wire may be
connected to either the
BNC or the RJ45,
whichever is convenient.
NVT has screw-terminal
adaptors available for this
purpose. These adaptors
support up to four sets of wires, each up to 16AWG.
For IP-based CCTV applications, there are some network
configurations that are robust, and others that are not
recommended. In general, it is best to deploy a separate LAN
exclusively for video traffic. Although it is possible to place IP
cameras onto the end-user’s “Enterprise LAN”, there are
several disadvantages in doing so. These include:
Traffic Management Considerations
When sharing the resources of a LAN, the nature of the traffic
must be well understood for it to operate efficiently. For most
end-users, the business use of their LAN is constantly chang-
ing, critical for their day-to-day operations, and not managed
by the same group that manages their security. IP video can
often consume large amounts of bandwidth, which may or
may not be compatible with existing IT traffic.
Security Considerations
Most surveillance systems are installed specifically to protect
against breaches in security. A shared LAN provides potential
opportunities for unauthorized access to security assets.
Sniffing IP addresses can result in the unintended disclosure of
IP cameras or network vulnerabilities. Spoofing IP addresses
could result in the disruption of recording.
If you must pass IP camera video through “public”
LANs, NVT recommends that video be recorded prior to
leaving the secure LAN. Then encrypt it by using a
Virtual Private Network (VPN) so that neither the video,
nor its addressing is readable on the LAN. Many low-
cost routers support VPNs.
NV-BNCT
NV-EC4BNC
NV-BNCA
NV-RJ45A
