A null modem adapter

Null modem is a communication method to connect two DTEs (computer, terminal, printer etc.) directly using a RS-232 serial cable. The original RS-232 standard only defined the connection of DTEs with DCEs i.e. modems. With a null modem connection the transmit and receive lines are crosslinked. Depending on the purpose, sometimes also one or more handshake lines are crosslinked. Several wiring layouts are in use because the null modem connection is not covered by a standard. Download high resolution version (640x640, 58 KB)null modem adapter Source: Image taken by Dori License: Public Domain This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... Download high resolution version (640x640, 58 KB)null modem adapter Source: Image taken by Dori License: Public Domain This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... DTE: Abbreviation for data terminal equipment. ... A computer was, till a decade back, only a device or machine for processing information from data according to a program — a compiled list of instruction. ... The term Terminal can be used in several way and includes various topics: Usually terminal means forming or pertaining to an end. ... A computer printer is a computer peripheral device that produces a hard copy (permanent human-readable text and/or graphics, usually on paper) from data stored in a computer connected to it. ... RS-232 (also referred to as EIA RS-232C or V.24) is a standard for serial binary data interchange between a DTE (Data terminal equipment) and a DCE (Data communication equipment). ... Serial is a term, originating in literature, for a format by which a story is told in contiguous installments in sequential issues of a single periodical publication. ... A cable is two or more wires bound together which may be bare, covered or insulated. ... The three-letter acronym DCE may stand for: Data Circuit-Terminating Equipment (DCE), also Data Communications Equipment (DCE) and Data Carrier Equipment (DCE). ... A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates a carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ... In communications and information processing, a transmitter (sometimes abbreviated XMTR) is an object (source) which sends information to an observer (receiver). ... The word receiver has a number of different meanings: In communications and information processing, a receiver is the recipient (observer) of a message (information), which is sent from a source (object). ... Shaking with the right hand while delivering a certificate with the left. ... The word standard has several meanings: Originally, standard referred to a conspicuous object used as a rallying point in battle. ...

Null modems are commonly used for file transfer between computers, or remote operation. Under the Microsoft Windows operating system, the direct cable connection can be used over a null modem connection. The later versions of MS-DOS were shipped with the InterLnk program. Both protocols allow the mapping of a hard disk on one computer as a network drive on the other computer. No networking hardware (such as a network interface card or a modem) is required for this. Microsoft Windows is a range of operating environments and operating systems for personal computers and servers. ... In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ... Direct Cable Connection, or DCC, is a feature of Microsoft Windows 95, 98, ME, XP, and 2000 that allows a computer to transfer and share files (or connected printers) with another computer, via a connection using either the serial, parallel, infrared IrDA, or USB ports of each computer. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... A list of DOS commands for Microsofts DOS operating system follows. ... The word protocol derives from a Greek phrase meaning first leaf, referring to the first draft of a treaty. ... Typical hard drives of the mid-1990s. ... Hardware is equipment such as fasteners, keys, locks, hinges, latches, corners, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts, especially when they are made of metal. ... A transitional network card with both BNC Thinnet (left) and Twisted pair (right) connectors. ...

The popularity and availability of faster information exchange systems such as ethernet made the use of null-modem cables less common. Nowadays, such a cable can still be useful to kernel hackers though, since it allows to remotely debug a kernel with a minimum of device drivers and code (a serial driver mainly consists of two FIFO buffers and an interrupt service routine). ddb or KGDB can be used to remotely debug BSD systems, for instance. This can also provide a serial console through which the in-kernel debugger can be dropped to in case of kernel panics, in which case the local monitor and keyboard may not be usable anymore (the X11 server reserves those resources if a GUI is used, and dropping to the debugger in the case of a panic won't free them). Ethernet is a frame-based computer networking technology for local area networks (LANs). ... The word kernel has a a variety of meanings in a several fields. ... FIFO is an acronym for First In, First Out. ... ddb consists of the BSD in-kernel debugger. ... BSD redirects here; for other uses see BSD (disambiguation). ...

Null modem cables and zzz adapters

A null modem cable is an RS-232 serial cable where the transmit and receive lines are crosslinked. In some cables there are also handshake lines crosslinked. In many situations a straight through serial cable is used, together with a null modem adapter. The adapter contains the necessary crosslinks between the signals. A serial cable is a cable that can be used to transfer information between two devices. ... This mains power plug travel adaptor allows European or British plugs to be inserted into American or Australian sockets An adapter or adaptor is a device used to match the physical or electrical characteristics of two different things so that a connection may be made between them. ...

Null modem cable pin mapping

This is one very common mapping which will work with software that relies on proper assertion of the CD signal.

Here is another pin connection diagram for a null modem: Example of a Null Modem File links The following pages link to this file: Null modem ...

See also

• Serial cable
• LapLink cable (can be seen as a parallel equivalent to a serial null modem cable)
• Direct cable connection
• Client-Server
• InterLnk
• USB
• Wi-Fi
• Bluetooth
• WLAN
• Network bridge
• Debugging

A serial cable is a cable that can be used to transfer information between two devices. ... A LapLink cable is a cable that allows one to connect two computers together to establish a direct cable connection. ... Direct Cable Connection, or DCC, is a feature of Microsoft Windows 95, 98, ME, XP, and 2000 that allows a computer to transfer and share files (or connected printers) with another computer, via a connection using either the serial, parallel, infrared IrDA, or USB ports of each computer. ... Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... A list of DOS commands for Microsofts DOS operating system follows. ... Type A USB connector Dual images of the two Type B USB connectors, mini and full size, side and front view, compared with a U.S. 5¢ piece (nickel) in both images for scale. ... Wi-Fi (sometimes written Wi-fi, WiFi, Wifi, wifi) is a trademark for sets of product compatibility standards for wireless local area networks (WLANs). ... This article is about the Bluetooth wireless specification. ... Wikipedia does not yet have an article with this exact name. ... A network bridge connects multiple network segments (network domains) along the data link layer. ... Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware thus making it behave as expected. ...

External links

• http://ourworld.compuserve.com/homepages/harburg/Link2PCs.htm
• http://www.unh.edu/helpdesk/webdoc/14.227.html
• http://www.angelfire.com/ma/mantasdos/interlnk.html
• http://www.ms-dos.com/dos-i/intexe-i.htm
• http://www.daniel-hertrich.de/rs232/
• http://www.nullmodem.com/NullModem.htm
• http://www.lammertbies.nl/comm/info/RS-232_null_modem.html