| Term |
Definition |
| R Reference Point |
In Integrated Service Digital Network technology the point at which non ISDN terminals are connected, via a terminal adapter, to an ISDN interface. |
| RACE |
Research on Advanced Communication for Europe. |
| Radial Wiring |
A wiring scheme in which all wires run from a single point to their destination by the shortest route. |
| RADLS |
Rate Adaptive Digital Subscriber Lines - A variation of DSL that uses carrierless amplitude phase modulation, divides the available frequencies into discrete sub-channels and also maximizes performance by adjusting the transmission to the quality of the phone line while in use. |
| RAM |
Random Access Memory - RAM is the main memory in the computer. It is called "random" because any random address can be accessed in an equal amount of time. |
| RAMDAC |
Random Access Memory Digital to Analog Converter. |
| Rate of Information Transfer |
The amount of information transferred within a system in unit time. |
| RBW |
Resolution Bandwidth. |
| RDS |
Radio Data Signal. |
| Reachable Node |
Any node (in a packet switched network) to which a specific node can direct packets. |
| Real-time Processing |
Processing that takes place at the same "real world" time that a transaction occurs. Such systems may also be referred to as event driven systems. |
| Receiver |
A device whose purpose is to capture transmitted signal energy and convert that energy for useful functions. In fiber optic systems, an electronic component that converts light energy to electrical energy. |
| Receiver Clock |
The electronics in a receiving interface which determines where one bit ends and the next starts. May have to be (in synchronous transmission) synchronized with the transmitters clock. |
| Redundancy |
When used in connection with a transmission control protocol refers to all the control bits which can (will) be removed with out loss of transmitted information. |
| Reference Noise |
A specific level of transmission circuit noise against which all other noise levels can be compared. |
| Reflection |
A return of electromagnetic energy that occurs at an impedance mismatch in a transmission line. |
| Refractive Index |
The ratio of the speed of light in a vacuum to its velocity in a transmitting medium, such as an optical fiber core. |
| Regeneration |
The process of recognizing and reconstructing a digital signal so that the amplitude, waveform and timing are constrained within stated limits. |
| Regenerator |
A digital repeater which receives signals and regenerates them before retransmission. By this process all effects of external noise and transmission distortion can be removed. Is often referred to simply as a repeater. |
| Register |
A temporary electronic data storage device. |
| Relative Transmission Level |
A measure of transmission medium quality. The power level of a fixed frequency transmission at a specific point is compared with the power level for the same frequency at a reference point. The reference point is normally the source transmission interface. |
| Relay |
i. A device which receives transmissions from one communications channel and retransmits them into another channel. The device is used to extend communications transmission distances. ii. An electrically operated switch. |
| Renpac |
A CCITT X.25 packet switched network operated in Brazil. |
| Repeater |
A device which receives a signal, performs some function (amplify or regenerate) and then retransmits it. In a data sense it is considered to be a bit store and forward device. |
| Residual Subcarrier |
This is the amount of color subcarrier information present in white, gray, or black areas of a composite color video signal (ideally, there is none present). |
| Return Bandpass |
The frequency range in a broadband transmission system which is used to receive signals. |
| Reverse Channel |
A facility in certain modems which allows for reception of low speed controlling information on the transmit line of a half duplex service. The slow speed signals are received at the same time as the high speed signals are being transmitted. This process allows for a certain level of full duplex operation on a half duplex line. |
| Reverse Interrupt Character |
A control sequence signal sent by a receiver back to a transmitter (during reception of transmitted data) requesting that transmission be stopped so that it (the receiver) can transmit a higher priority message. |
| Reversed Pair |
A wiring error in twisted pair cabling where the conductors of a pair are reversed between connector pins at each end of a cable. |
| RF |
Radio Frequency. |
| RFI |
Radio Frequency Interference. |
| RFITL |
Rural fiber in the loop. |
| RGB |
Abbreviation of red/green/blue - Method of connecting a colour screen to a computer, involving three separate signals: red, green, and blue. All the colours displayed by the screen can be made up from these three component colours. |
| RIBBON |
Up to 12 fibers clad in a single fiber. |
| Ring Polling |
The process whereby devices are polled sequentially to determine if they have data to transmit. When the last device has been polled and any data transmitted the process returns to the first in the sequence. |
| Ring Topology |
The network structure whereby connection between devices is accomplished by arranging them in a physical ring. |
| RISC |
Reduced instruction-set computer - A microprocessor (processor on a single chip) that carries out fewer instructions than other (CISC) microprocessors in common use in the 1990s. Because of the low number and the regularity of machine code instructions, the processor carries out those instructions very quickly. |
| RLL |
Radio in the Local Loop. |
| RM |
Resource Management cell - A cell used for carry network resource management information, such as available buffer space, residual bandwidth and indicate the presence of any congestion in the network. RM cells are injected in regular data cells streams in order to monitor and report the network conditions. A value of 6 is reserved in the PTI field of an ATM cell to indicate an RM cell. |
| ROLC |
Routing Over Large Clouds - Protocol specifications defined by the IETF for supporting efficient IP routing over large networks. |
| ROM |
Read Only Memory. |
| Round Trip Delay |
The time it takes for an electrical signal to travel from one end of a medium and back. |
| Route |
The path through a network which will be used to transfer transmission frames from source to destination. |
| Route Table |
A data base used by the network layer in a layered architecture to store information against which routing decisions will be made. |
| Route Through |
The process whereby intermediate nodes transfer messages from source to destination. This process is normally referred to as packet switching. |
| Router |
A special-purpose hardware device(or software package) that handles the connection between two or more networks. Routers spend all their time looking at the destination addresses of the packets passing through them and deciding which route to send them on. |
| RPC |
Remote Procedure Call. |
| RSSI |
Receive Signal Strength Indicator. |
| RSVP |
Resource reservation Protocol - A protocol developed for supporting different QoS classes for IP applications. |
| RTCP |
Real-Time Control Protocol - The control protocol for RTP, RTCP is used for control and diagnostic on RTP sessions. Like RTP, RTCP typically runs on top of UDP and is defined in the IETF RFC1889. |
| RTP |
Real-Time Protocol - A transport protocol designed to provide end-to-end delivery services for data withreal-time characteristics. RTP typically runs on top of UDP. Defined in the IETF RFC1889. |
| Runt Frame |
An Ethernet frame that is less than the minimum length of 64-bytes. In a half-duplex Ethernet environment, runt frames are almost always caused by collisions. If runt frames occur when collisions are not high or in a full-duplex Ethernet environment, then they are probably the result of underruns or bad software on a network interface card. |
| Rx |
Receive. |
