EIA-485 (formerly RS-485 or RS485) is an OSI Model physical layer 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 (35Mbit/s up to 10m and 100kbit/s at 1200m), and since it uses a differential balanced line over twisted pair (like EIA-422), it can span relatively large distances (up to 4000 feet or just over 1200 metres). EIA-485 only specifies electrical characteristics of the driver and the receiver. It does not specify or recommend any data protocol. The Open Systems Interconnection Reference Model (OSI Model or OSI Reference Model for short) is a layered abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnect initiative. ... The physical layer is level one in the seven level OSI model of computer networking. ... The article on electrical energy is located elsewhere. ... In engineering and manufacturing, the term specification has the following meanings: Technical requirement An essential technical requirement for items, materials, or services, including the procedures to be used to determine whether the requirement has been met. ... A wire is a single, usually cylindrical, elongated strand of drawn metal. ... Duplex is the having of two principal elements or parts. ... In telecommunications and computer science, serial communications refers to any data transmission scheme in which data is sent one symbol at at time, sequentially over a communications channel. ... In communications or computer systems, a configuration is an arrangement of functional units according to their nature, number, and chief characteristics. ... A local area network (LAN) is a computer network covering a local area, like a home, office or small group of buildings such as a college. ... Data transmission is, very generally speaking, the conveyance of any kind of information from one space to another. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... A differential can mean one of several things: Differential (mathematics) Differential (mechanics) Differential signaling is used to carry high speed digital signals. ... In telecommunication, a balanced line is a transmission line consisting of two conductors in the presence of ground, capable of being operated in such a way that when the voltages of the two conductors at all transverse planes are equal in magnitude and opposite in polarity with respect to ground... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ... EIA-422 (formerly RS-422) is a serial data communication protocol which specifies 4-wire, full-duplex, differential line, multi-drop communications. ... This article is about a foot as a unit of length. ... The metre (American spelling: meter), symbol: m, is the basic unit of distance (or of length, in the parlance of the physical sciences) in the International System of Units. ... A datum is a statement accepted at face value (a given). Data is the plural of datum. ... For meanings in specific fields, see protocol (computing) or protocol (cryptography). ...

In contrast to EIA-422, which has a single driver circuit which cannot be switched off, EIA-485 drives need to be put in transmit mode explicitly by asserting a signal to the driver. This allows EIA-485 to implement star network topologies using only two lines. Device driver vehicle driver (driving) JDBC driver - a software that allows applications to connect to a database a kind of sail on a sailboat (driver (sail)) The golf club usually used for the first shot on a par 4 or 5 hole. ... There are many kinds of circuit An electric circuit interconnects electrical elements. ... In communications and information processing, a transmitter (sometimes abbreviated XMTR) is an object (source) which sends information to an observer (receiver). ... A signal may refer to: an abstract element of information, or, more exactly, usually a flow of information (in either one or several dimensions). ... A computer network with a star network topology, in its simplest form, consists of one central, or hub computer which acts as a router to transmit messages. ... A network may be represented as a collection of nodes, some of which are connected by links. ...

EIA-485, like EIA-422 can be made full-duplex by using four wires, however, since EIA-485 is a multi-point specification, this is not necessary in many cases. Duplex is the having of two principal elements or parts. ...

It is worthwhile to note that SCSI-2 and SCSI-3 (for instance) use this specification to implement the physical layer. SCSI stands for Small Computer System Interface, and is a standard interface for transferring data between devices on a computer bus. ... The physical layer is level one in the seven level OSI model of computer networking. ...

External link

• What is RS485? (http://rs485.ca/rs485is.html)