Introduction to ISDN Line

Find here ISDN Network, introduction to ISDN line, bri, t1 lines, d1 lines, primary rate interface, connection time and setup instructions. The regular phone line, which is used at home and offices is an analogue phone line. Your voice is picked up by telephone mouthpiece and then sent down the phone line as an analogue wave. Regular modem converts the digital signals of the computer into the analogue waves, which then travels on the regular phone lines.

 

At the other end, modem receives that analogue signals and then convert back into the digital signals that are understandable by a computer ISDN network is a digital communication system that is capable of producing the maximum transmission speed of 1.4Mbps. 128Kbps speed is however more common in the digital technology. It's a international standard for sending data, voice, video over regular digital telephone lines. ISDN uses UTP (unshielded twisted pair cable) for transmission.

Types of ISDN Network

There are two basic types

• Basic Rate Interface (BRI) – It consists of two 64 B-channels and one D-channel for transmitting control information.
• Primary Rate Interface (PRI) -- It consists of 23 B-channels and one D-channel (for U.S.) or 30 B-channels and one D-channel (for Europe).

The actual version of ISDN employs base band transmission. Another version, called B-ISDN, uses broadband transmission, which is able to support transmission rate of 1.5 Mbps. B-ISDN mainly requires fiber optic cables.

To access the B channel, it is necessary to subscribe the ISDN phone line. Customers are also required to have some special ISDN devices, which are known as terminal adapters, which are used to communication with the telephone company switch or other ISDN devices.

How ISDN Works

In an analog network, a regular telephone line that is provided by the telephone company supports a single transmission channel, which normally can carry only one service, voice, data or video at a single time. With ISDN, this same pair telephone line is logically divided into the multiple channels. A typical line has two channels.

The first type of channel is called B channel. This channel can carry about 64Kbps of data. Typical ISDN line has 2 B channels. One channel is used for voice and other channel is used for data communication. This data/voice transmission process occurs on the regular one pair copper wire.

The second type of channel is used for link and call setup. This channel is known as D channel or Delta Channel.

The third channel has only 16Kbps of bandwidth.

Advantages

Speed

There is an upper limit of the speed in the commonly used dial up modems, which is 56kbps. But due to the quality and other factor, the maximum attainable speed is 45kbps.

ISDN allows multiple digital channels to operate simultaneously through the same regular one pair copper wire. If the telephone company supports the digital connections then a change can occur. The digital signals instead of the analogue signals, transmitted across the telephone line. In the digital scheme, there is much more data transfer rate than the analog lines.

Multiple Devices

A separate telephone line is required for using the fax, telephone, computer, router and live video conferencing systems. A separate line is required for each device. ISDN network lines can handle the multiple devices on the single line. Up to eight devices such as, computer, faxes, cash registers, credit card readers or other devices can directly be connected to a single ISDN line, all these devices can work simultaneously.

Connection Time

V.34 modems typical take 30-60 seconds to establish a connection and on the other end an ISDN call usually takes less than 2 seconds to establish a connection.

Disadvantages

There are some disadvantages of the ISDN lines, which I have discussed below.

1. ISDN is more expensive than the Plain old telephone system.
2. The telephone company and the ISDN user both are required to have the specialized digital devices.

ADSL VS ISDN

There is a noticeable difference between the two services.

• ISDN provides two voice channels or one 128Kbps data channel while ADSL is basically a data pipe.
• The power for ADSL is sent by carrier over copper wire; as with the local phone service. The line works even when local power fails. This is an advantage over the ISDN lines, which requires the local power supply.

Introduction to the Network Communication Devices

In this tutorial you will learn get the basic introduction to network devices such as nic adapters, routers, hubs, switches, modems, communication cables, lan/wan routers, gateway and other devices. A network is consists of a larger number of the communication devices. The simplest device that is used in the communication is the NIC adapter which is attached with the every computer in a network. If you want to build a LAN, you will need to have computers, hubs, switches, network adapters, UTP/STP cables, routers, internal/external modems, connectors, cable testers and clipping tool.  

On the other hand if you need to build WAN, you will need to have routers, switches, dedicated or leased telephone lines such as ISDN lines, frame relay connection and other types of wan communication connections. 

There are different communication mediums such as Ethernet cables, copper wire, coaxial cable, fiber optic cables, leased telephone lines and ever air is also a communication medium for the satellite communication. The most common networking medium is the LAN is the Ethernet cable (UTP/STP), which is used in the star topology. Hub is a central device of a network and every computer in a network is directly connected with the hub.

If the hub fails to work, the communication between the computers stops till the hub again starts working. Hub broadcasts the data to its every port, and then finding the destined computer, the data sent toward it. The switch is an advance form of the hub similar in functions but the advanced switches has a switching table in them. A advanced switch stores the MAC address of every attached computer and the data is only sent to the destined computer, unlike the hubs where data is sent to all ports. A router is a key device in the internet communication and wan communication system. A router has software called routing table and the source and destination addresses are stored in the routing table.

A router connects two logically and physically different networks. Router finds the IP address of the next hop (next router) and the data is sent toward it and so on. The well known routers developing companies are Cisco systems, Nortel, DLink and others. Every ISP, banks, corporate offices and multinational companies use routers for LAN and WAN communications and communication in their private networks. A gateway can be device or software in a network.

A gateway device connects the LAN with the internet. A gateway is directly exposed to the internet so it should be securely configured and in and out traffic should be monitored. If you are using DSL connection, you must need a DSL modem in your network. The telephone line is connected with the DSL modem and UTP/STP cable attaches your computer with the DSL modem. Modems are the devices that are used to modulate and demodulate the data. They convert analogue signals to digital and digital signals to analogue so that signals can travel on the telephone lines.

There are certain types of the cables that are used to connect two or more computers in a network. Fiber optic cable acts as a backbone between the ISPs and corporate offices. Data travels at the speed of light on the fiber optic cables. The cost and the installation cost of the fiber optic cable is very high but it is becoming very popular in the home networking and LANs also. In the local area networking, 10baseT/CAT5 cable is most commonly in use.

A server is a computer in network that provides services to the client computers such as logon requests processing, files access and storage, internet access, printing access and many other types of services. Servers are mostly equipped with extra hardware such as plenty of external memory (RAM), more data store capacity (hard disks), high processing speed and other features.