RAM :
Random Access Memory. The place in a computer where the operating system, application programs, and data in current use are kept temporarily so that they can be quickly reached by the computer's processor.
RARP :
Reverse Address Resolution Protocol. For host machines that don't know their IP address.
RCA :
The Radio Corporation of America; conveniently used to describe phono jack and plug, one of the audio/video connectors.
Resolution :
Expressed by TV lines or pixels, it indicates the quality level of video images.(e.g. 720 x 576)
720 = number of points in each row that make up the picture
576 = number of rows
RF :
Radio Frequency.
RG Cable :
RG stands for Radio Guide (meaningless anymore). The most common RG designations are RG-6, RG-8, RG-11, RG-58 and RG-59.
RoHS (Restriction of Hazardous Substances) :
This directive restricts the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment. The six materials are Lead, Mercury, Cadmium, Hexavalent chromium, Polybrominated biphenyls (PBB), and Polybrominated diphenyl ether (PBDE).
Router :
A device that forwards data packets along networks. Typically when referred to in CCTV installations, a router is used to connect a surveillance DVR and a computer to a single internet connection. A router can also be used to connect multiple IP based security cameras to a single internet connection.
RS-232 :
RS-232 is a communications standard for serial communications between devices. In CCTV, this can be communication between a contoller and a surveillance camera. The RS-232 standard allows for the connection of two devices through a serial link, and is the protocal used for serial connections in computers. RS-485 allows for serial connections between more than 2 devices on a networked system and is defined below.
RS-485 :
RS485, also referred to as EIA-485 is a communications standard for serial communication between devices. When talking about surveillance systems, RS-485 is typically used as the protocal to allow computers and remote controllers to control the activity of cameras such as pan, tilt, rotate, and zoom operations. RS485 is an updated version of the original serial protocol, RS-232.
RG59 :
A type of CCTV Coaxial cable used to transmit cctv camera video signals to a CCTV System.
Radio Frequency Identification :
A method of reading a card using radio frequency energy to transmit information from the card to a reader. See Proximity.
Random Access Memory (RAM) :
Randomly addressable, readable and writable memory (either volatile or nonvolatile) whose contents may be read or be altered at will.
Reader :
A device that "receives" an identification code from a card, key tag, magnetic stripe card, bar code card, or related item.
Relay :
A device that is capable of opening a normally-closed circuit or closing a normally-open circuit. When the relay is not energized, the normally-closed circuit is complete and the normally-open circuit is open. When the relay is energized, it switches roles, opening the normally-closed circuit and closing the normally-open circuit. This dual nature of a relay allows for two types of applications: a device may be attached to the normally-closed circuit so that the device is always on until the relay energizes to turn it off, or a device may be attached to the normally-open circuit so that the device is always off until the relay energizes to turn it on.
Request to Exit (RTE) :
A signal that informs the controller that someone has requested to exit from a secure area.
REX :
An acronym for Request to Exit. See Request to Exit.
Read Only Memory (ROM) :
Nonvolatile memory whose contents are programmed into the ROM when the ROM is made, and therefore cannot be altered. ROM is typically used to store programs and fixed data sets.
Real Time Command :
A command that is executed immediately, with no time delay.
RFID :
See Radio Frequency Identification.
ROM :
See Read Only Memory.
RS-232 :
A serial communication protocol used for connecting data terminal devices. RS-232 is the most commonly used communication protocol.
RS-485 :
A serial communication protocol used for multi-drop communication applications. It is used for higher speed and longer distance communications.
RTE :
See Request to Exit.
