 to one another in a closed logical circle, with access to the medium passing sequentially from one station to the next by means of polling from a master station or by passing an access token from one station to another. Also called a loop. ring in/ring out A connection on a token-ring MAU that is used to tie multiple MAUs into a larger ring. ringing signal Any AC or DC signal transmitted over a line or trunk for the purpose of alert- ing a party at the distant end of an incoming call. The signal can operate a visual- or sound- producing device. RIP (Routing Information Protocol) A routing protocol used on TCP/IP networks that distributes the addresses of reachable networks and metrics reflecting the degree of difficulty involved in reaching particular networks form particular locations. RJ-11 A standard four-wire modular connector used with telephones. RJ-45 An eight-wire modular connector used with UTP. RO (receive only) (1) A printer terminal without a keyboard for data entry. (2) A satellite earth station that can receive but not transmit signals. ROADM (reconfigurable optical add/drop multiplexer) An add/drop mux that software based and adds the capability to switch between different networks. ROADMs can switch traffic at both the SDH/SONET and wavelength layers. robot An easily reprogrammable, computer-controlled device that can physically manipulate its surroundings. rotary dial calling A system that accepts dialing from conventional rotary dial sets that gen- erate pulses. router A device that connects two LAN segments that use similar or different architectures at the OSI network layer (Layer 3). A router determines the most efficient route for passing data through an internet. Packets that contain a network address different from the originating PC's address are forwarded to an adjoining network. Multiprotocol routers can handle this job for two or more protocols simultaneously. routing algorithm routing algorithm A formula that uses metrics (e.g., path length, destination, next-hop associations, reliab