 - A null modem cable allows you to connect your PC to another nearby PC or serial device using its modem protocol. A popular use of null modem cables is for setting up "head-to-head" gaming between two players at different computers in the same room. (A null modem cable is limited to 30 feet in length.)
The standard RS-232C serial communications interface defines a signal protocol between a Data Terminal Equipment (DTE) - usually your PC - and a Data Communications Equipment (DCE) - or your modem. The signals are transmitted on a set of lines, each of which has a function in the "talk" that the DTE and DCE do back and forth. One line each way is for data; the other lines are for different "statements" that one end of the communication sends to the other. For example, the DTE sends the DCE (usually a modem) a "Request to Send" signal on the RTS line and the DCE replies with a "Clear to Send" signal on the CTS line. After a series of similar exchanges, the DTE sends data on the line devoted to transmitting data (which for the DCE is a line for receiving data from the DTE).
Since a modem or DCE is not really needed to interconnect your PC with another local serial device, the DTE interface can be used by both your PC and the attached serial device. However, the DTE interface is designed to work with a DCE device. What a null modem cable does is to make the other end of the PC or device's DTE interface look like a DCE interface.
A null modem cable is sometimes called a crossover cable.
 |
Learn more about LANs (Local Area Networks) |
| LAN administration guide: LAN administration is an arduous task and your responsibilities often involve many different aspects and may include many tasks. This guide will help you with each step and task. |
| LAN network design considerations: What are the steps to be kept in mind while designing a network having three hundred nodes within a three-floor building and one server room? |
| 10 Gigabit Ethernet tutorial: Connecting data centers, storage, LAN and beyond: Learn how to choose 10 Gigabit Ethernet cabling and components, why new Gigabit Ethernet protocols will improve performance, and how it can all result in data center optimization. |
| Best practices for securing your wireless LAN: Learn best practices for securing a wireless LAN (WLAN) in the enterprise, from systematically monitoring your WLAN for intruders to protecting users and the network itself. |
| A basic virtualized enterprise -- from 'Network Virtualization': Learn why and how to virtualize the network in this chapter from 'Network virtualization' by Victor Moreno and Kumar Reddy. |
| Configuring VLANs: Learn how to configure a virtual LAN (VLAN) in this step-by-step, automated, 15-minute demo. |
| Network administration guide: Network administration responsibilities, such as network design, troubleshooting, backup, documentation, security, and managing users are discussed in this guide. |
| CONTRIBUTORS: |
Paul Ruffolo |
| LAST UPDATED: |
07 Aug 2006
|
 |
Do you have something to add to this definition? Let us know.
Send your comments to techterms@whatis.com
|
|
More resources from around the web:
|
 |
 |
| |
RELATED GLOSSARY TERMS
| Terms from Whatis.com − the technology online dictionary |
 |
32-bit IP addressing
(SearchNetworking.com)
32-bit IP addressing is the IP address scheme used in Internet Protocol 4 (IPv6 uses a 128-bit system)... (Continued)
|
|
ARCNET
(SearchNetworking.com)
ARCNET is a widely-installed local area network (LAN) technology that uses a token-bus scheme for managing line sharing among the workstations and...
|
|
|
Show me everything on 