69
AXIS 242S IV - Glossary
RS-232
- A long-established standard that describes the
physical interface and protocol for low-speed serial data
communication between devices. This is the interface that
e.g. a computer uses to talk to and exchange data with a
modem and other serial devices.
RS-422
- A serial data communication protocol that
specifies 4-wire, full-duplex, differential line, multi-drop
communications. It provides balanced data transmission
with unidirectional/non-reversible, terminated or
non-terminated transmission lines. RS-422 does not allow
multiple drivers, only multiple receivers. Maximum
recommended range is 4,000 feet (1200 meters).
Maximum recommended baud rate is 10Mbit/s.
RS-485
- An upgraded version of RS-422 that supports
up to 32 devices on the same connection. RS-485 is an
electrical specification of a two-wire, half-duplex,
multipoint serial connection. It enables the configuration
of inexpensive local networks and multidrop
communications links. It offers high data transmission
speeds (up to 10Mbit/s), and as it uses a differential
balanced line over twisted pair (like RS-422), it can span
relatively large distances (4000 feet or 1200 meters).
RS-485 only specifies the electrical characteristics of the
driver and the receiver. It does not specify or recommend
any data protocol.
RTCP (Real-Time Control Protocol)
- RTCP provides
support for real-time conferencing of groups of any size
within an intranet. This support includes source
identification and support for gateways like audio and
video bridges as well as multicast-to-unicast translators.
It offers quality-of-service feedback from receivers to the
multicast group as well as support for the synchronization
of different media streams.
RTP (Real-Time Transport Protocol)
- An Internet
protocol for the transport of real-time data, e.g. audio and
video. It can be used for media-on-demand as well as
interactive services such as Internet telephony.
RTSP (Real Time Streaming Protocol)
- A control
protocol, and a starting point for negotiating transports
such as RTP, multicast and Unicast, and for negotiating
codecs. RTSP can be considered a "remote control" for
controlling the media stream delivered by a media server.
RTSP servers typically use RTP as the protocol for the
actual transport of audio/video data.
Router
- A device that determines the next network point
to which a packet should be forwarded on its way to its
final destination. A router creates and/or maintains a
special routing table that stores information on how best
to reach certain destinations. A router is sometimes
included as part of a network switch. See also
Switch
.
Security surveillance -
Network video's advanced
functionality makes it highly suited to the applications
involved in security surveillance. The flexibility of digital
technology enhances security personnel's ability to
protect people, property and assets. Such systems are
therefore an especially attractive option for companies
currently using CCTV.
Server
- In general, a server is a computer program tha
provides services to other computer programs in the same
or other computers. A computer running a server program
is also frequently referred to as a server. In practice, the
server may contain any number of server and client
programs. A web server is the computer program that
supplies the requested HTML pages or files to the client
(web browser).
Sharpness
- This is the control of fine detail within a
picture. This feature was originally introduced into color
TV sets that used notch filter decoders. This filter took
away all high frequency detail in the black and white
region of the picture. The sharpness control attempted to
put some of that detail back in the picture. Sharpness
controls are mostly superfluous in today's high-end TVs.
The only logical requirement for it nowadays is on a VHS
machine.
Simplex
- In simplex operation, a network cable or
communications channel can only send information in
one direction. See also
Full-duplex
.
SMTP (Simple Mail Transfer Protocol)
- Used for sending
and receiving e-mail. However, as it is "simple," it is
limited in its ability to queue messages at the receiving
end, and is usually used with one of two other protocols,
POP3 or IMAP. These other protocols allow the user to
save messages in a server mailbox and download them
periodically from the server.
SMTP authentication
- An extension of SMTP, where the
client is required to log into the mail server before or
during the sending of email. It can be used to allow
legitimate users to send email while denying the service to
unauthorized users, such as spammers.
SNMP (Simple Network Management Protocol)
- SNMP
forms part of the Internet Protocol suite, as defined by the
Internet Engineering Task Force. The protocol can support
monitoring of network-attached devices for any
conditions that warrant administrative attention.
Sockets
- Sockets are a method for communication
between a client program and a server program over a
network. A socket is defined as "the endpoint in a
connection." Sockets are created and used with a set of
programming requests or "function calls" sometimes
called the sockets application programming interface
(API).
SSL/TSL
(Secure Socket Layer/Transport Layer Security)
- These
two protocols (SSL is succeeded by TSL) are cryptographic
protocols that provide secure communication on a
network. SSL is commonly used over HTTP to form
HTTPS, as used e.g. on the Internet for electronic financial
transactions. SSL uses public key certificates to verify the
