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13. Glossary
Dual Stream:
Dual stream is a technology used to record high resolution video locally
while transmitting a lower resolution stream over the network. The two streams are
generated by the DVR, with the main stream having a maximum resolution of 4CIF and
the sub-stream having a maximum resolution of QCIF.
DVR:
Acronym for Digital Video Recorder. A DVR is device that is able to accept video
signals from analogue cameras, compress the signal and store it on its hard drives.
HDD:
Acronym for Hard Disk Drive. A storage medium which stores digitally encoded
data on platters with magnetic surfaces.
DHCP:
Dynamic Host Configuration Protocol (DHCP) is a network application protocol
used by devices (DHCP clients) to obtain configuration information for operation in an
Internet Protocol network.
HTTP:
Acronym for Hypertext Transfer Protocol. A protocol to transfer hypertext
request and information between servers and browsers over a network
PPPoE:
PPPoE, Point-to-Point Protocol over Ethernet, is a network protocol for
encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It is used
mainly with ADSL services where individual users connect to the ADSL transceiver
(modem) over Ethernet and in plain Metro Ethernet networks. Not used in UK.
DDNS:
Dynamic DNS is a method, protocol, or network service that provides the
capability for a networked device, such as a router or computer system using the Internet
Protocol Suite, to notify a domain name server to change, in real time (ad-hoc) the active
DNS configuration of its configured hostnames, addresses or other information stored in
DNS.
NTP:
Acronym for Network Time Protocol. A protocol designed to synchronise the
clocks of computers over a network.
NTSC:
Acronym for National Television System Committee. NTSC is an analogue
television standard used in such countries as the United States and Japan. Each frame of
an NTSC signal contains 525 scan lines at 60Hz.
PAL:
Acronym for Phase Alternating Line. PAL is also another video standard used in
broadcast televisions systems in large parts of the world. PAL signal contains 625 scan
lines at 50Hz. Used in the UK.
PTZ:
Acronym for Pan, Tilt, Zoom. PTZ cameras are motor driven systems that allow
the camera to pan left and right, tilt up and down and zoom in and out.
USB:
Acronym for Universal Serial Bus. USB is a plug-and-play serial bus standard to
interface devices to a host computer.
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