Sunday, June 14, 2009


LocalTalk is a network protocol that was developed by Apple Computer, Inc. for Macintosh computers. The method used by LocalTalk is called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). It is similar to CSMA/CD except that a computer signals its intent to transmit before it actually does so. LocalTalk adapters and special twisted pair cable can be used to connect a series of computers through the serial port. The Macintosh operating system allows the establishment of a peer-to-peer network without the need for additional software. With the addition of the server version of AppleShare software, a client/server network can be established. The LocalTalk protocol allows for linear bus, star, or tree topologies using twisted pair cable. A primary disadvantage of LocalTalk is speed. Its speed of transmission is only 230 Kbps.

Monday, June 8, 2009

Wireless LAN

Not all networks are connected with cabling; some networks are wireless. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite.Wireless networks are great for allowing laptop computers or remote computers to connect to the LAN. Wireless networks are also beneficial in older buildings where it may be difficult or impossible to install cables.

The two most common types of infrared communications used in schools are line-of-sight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network.

Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks.
Wireless LANs have several disadvantages. They provide poor security, and are susceptible to interference from lights and electronic devices. They are also slower than LANs using cabling.

Wednesday, June 3, 2009

Bluetooth Technology

First of all, I want to told you from where word “Bluetooth” came, it put on the name of a great Denmark king whose name was “Harald Bluetooth” a thousand years of ago. Now the question is, what is bluetooth technology, actually it is a technology which is used for low-power radio communications to wirelessly link phones, computers and other network devices over short distances. Initially it was developed for support of personal wireless devices including cell phones, PDAs, and wireless headsets.The signals that are transmitted through “Bluetooth” devices are short distance in nature, They diminishes after 10m(30 feet).The data transferred through Bluetooth devices is at a rate of less than 1Mbps.As I already told you “Bluetooth” devices works on the principle of radio communication systems, so it is not required that the two Bluetooth devices must be in line of sight of each other, they can be either in different rooms, as long as the received transmission is powerful enough.

Today,there are many bluetooth enabled devices exists such as phones, printers, modems and headsets etc. This technology is useful only when the Bluetooth enabled devices are present in low- bandwidth position. Today Bluetooth is mainly used in cell phones to transfer sound data, or text data with laptops, and from Bluetooth enabled devices.From the security point of view, the data transferred between blue tooth devices is encrypted through some custom algorithms so that it can be safely transmitted. Hence, we can say that data transferred through Bluetooth devices is secure.As, the work is going on the development of Bluetooth so that it can be made more faster,simpler in comparison to other wireless technology.