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Technical Glossary R - T

RADSL - Rate Adaptive Digital Subscriber Line. Transmission technology that supports both asymmetric and symmetric applications on a single twisted-pair telephone line. Allows adaptive data rates up to 7 Mbps.

RFI - Radio Frequency Interference. All computer equipment generates radio waves. Levels are regulated by the FCC.

Router - An intelligent device that can send or receive data over a wide area network. A router provides more sophisticated inter- communications than a bridge. Connects LANs by dynamically routing data according to network Layer 3.

RS-232 - An EIA standard defining the 25-position interface between DTE and DCE equipment used for low speed (below 20 Kbps) serial data transmission.

RS-366A - An EIA standard for defining the 25-position interface between DTE and data communications automatic calling equipment. Passes dialing information only.

RS-442/RS-449 - Uses a standard 37-pin connector and provides faster transmission than RS-232 over greater distances (4,000 ft.) through an improved electrical interface. Unpopular.

RS-530 - High-speed, 25-position interface for DTE equipment and data circuit terminating equipment (DCE) that employs serial binary data interface exchange. Developed to serve as a complement to the RS-232 and replacement for V.35 and RS-442/449 for data rates above 20 Kbps.

RSVP - Resource reservation setup Protocol. Provides priority data transmissions based on reservation protocol.

RT - Remote Terminal. The local loop can be terminated at RT. RTs are intermediate points closer to the customer premises to improve service reliability.

RTU - Remote Termination Unit. A device installed at the customer premises that connects to the local loop. Also referred to as the ATU-R.

SDH - Synchronous Digital Hierarchy. Based in part on SONET, SDH is an ITU standard for the interworking of ANSI and ITU transmission techniques.

SDSL - Symmetric Digital Subscriber Line. Provides high bandwidth, bi-directional transmission over one copper wire pair for T I or E 1 services.

Shared Diagnostic Control Panel (SDCP) - A feature that allows carrier-mounted DSUs and modems to share the same diagnostic control panel. Installed at eye level into one COMSPHERE 3000 Series Carrier, it controls and monitors the DSUs and modems in all the carriers in the cabinet. A single SDCP can control up to eight carriers, with a total of 128 DSUs (and if present, 123 DBMs) and modems.

Shared Diagnostic Unit (SDU) - A circuit card that plugs into a dedicated slot in the COMSPHERE 3000 Series Carrier to provide the shared diagnostic control panel and network management interfaces to the DSUs in the carrier.

It translates the network management protocol to the devices in the carrier and routes incoming messages to the appropriate slots.

SIP - SMDS Interface Protocol. A three-layer protocol implemented in SMDS networks.

SMDS - Switched Multimegabit Digital Services. A packet switching service connecting LANs.

SNA - Systems Network Architecture. A description of the logical structure and protocols that transmit information and control the operation on an IBM network.

Simple Network Management Protocol (SNMP) - A network management communications protocol originally developed by the Internet Engineering Task Force (IETF) for use on a TCP/IP network. SNMP was designed to let software and systems from various suppliers share the same information. It has now been expanded for general use in managing distributed network devices and applications.

SOHO - Small Office/Home Office.

SONET - Synchronous Optical NETwork. An ANSI standard for the transmission of digital data over optical networks.

Speaker Panel - An optional component that can be installed on the carrier to provide audio monitoring of any Model 3811 or 3911 dial/lease modem.

STS-1 - Synchronous Transport Signal 1. The fundamental SONET standard for transmission over optical fiber at 51.84 Mbps.

SU - Service User. The end user at the customer premises.

Subrate Multiplexing - The process of combining lower data rates into a single 64 Kbps channel signal.

Superframe - The framing format used in D4 transmission. See D4.

SWC - Service Wire Center.

Switched 56 Kbps Digital Service - A service provided by local exchange and interexchange carriers (LECs and IECs) that allows customers to use high-speed switched digital services without having to subscribe to private network services.

Synchronous Transmission - Data transmission that is synchronized by timing signals and usually transmitted in blocks rather than individual characters. This type of transmission is more efficient than asynchronous transmission.

Systems Network Architecture (SNA) - A description of the logical structure, formats, protocols, and operation sequences that transmit information and control the configuration and operation of an IBM network.

T1 - A term for a digital carrier facility used to transmit a DSI formatted digital signal at 1.544 Mbps. It is primarily used in the United States.

T3 - A digital carrier facility used to transmit a DS3 formatted signal at 44.736 Mbps.