introduction to isdn line

8/14/2019 Introduction to Isdn Line

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Vocational Training Course-2008

11INTRODUCTION TO ISDN LINE

Find here ISDN Network, introduction to ISDN line, bri, t1 lines, d1 lines, primary rateinterface, connection time and setup instructions. The regular phone line, which isused at home and offices is an analogue phone line. Your voice is picked up bytelephone mouthpiece and then sent down the phone line as an analogue wave.Regular modem converts the digital signals of the computer into the analoguewaves, which then travels on the regular phone lines. At the other end, modemreceives that analogue signals and then convert back into the digital signals that areunderstandable by a computer

ISDN network is a digital communication system that is capable of producing themaximum transmission speed of 1.4Mbps. 128Kbps speed is however morecommon 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 fortransmitting control information.

Primary Rate Interface (PRI) -- It consists of 23 B-channels and one D-channel (forU.S.) or 30 B-channels and one D-channel (for Europe).

The actual version of ISDN employs base band transmission. Another version, calledB-ISDN, uses broadband transmission, which is able to support transmission rate of1.5 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 knownas terminal adapters, which are used to communication with the telephone companyswitch or other ISDN devices.

How ISDN Works

In an analog network, a regular telephone line that is provided by the telephonecompany supports a single transmission channel, which normally can carry only one

AIR GWALIOR C.P.Harikumar-2008


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service, voice, data or video at a single time. With ISDN, this same pair telephoneline 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 ofdata. 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 processoccurs on the regular one pair copper wire.

The second type of channel is used for link and call setup. This channel is known asD 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 is56kbps. But due to the quality and other factor, the maximum attainable speed is45kbps.ISDN allows multiple digital channels to operate simultaneously through the sameregular one pair copper wire. If the telephone company supports the digitalconnections then a change can occur. The digital signals instead of the analoguesignals, transmitted across the telephone line. In the digital scheme, there is muchmore data transfer rate than the analog lines.

Multiple Devices

A separate telephone line is required for using the fax, telephone, computer, routerand 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 eightdevices such as, computer, faxes, cash registers, credit card readers or otherdevices can directly be connected to a single ISDN line, all these devices can worksimultaneously.

Connection Time

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

DisadvantagesThere 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 thespecialized 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



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service. The line works even when local power fails. This is an advantage over theISDN lines, which requires the local power supply.

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introduction to isdn line

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