Overview of ISDN Lines
Using internet is part of our lives now; we use it at home, collages and offices for different reasons. There are many ways with which internet reach to us, there are dial up connections which is more of old method for internet connectivity, Cable internet, DSL, Wireless internet, etc, ISDN is just another way to internet connectivity.
The landline numbers which are used at offices and homes are analogue lines, voice of speaker is picked up by telephone handset and then transfer over phone line as an analogue. Modems which are used in computers for internet connectivity converts digital signals from the computer into analogue signal so that these signals can travel through regular telephone lines. When modem receives analogue signals in return to from telephone lines, it convents these analogue signals into digital signals for computer to understand and process the information.
ISDN lines however are digital communication system. ISDN stands for INTEGRATED SERVICES DIGITAl NETWORK. ISDN networks are capable of generating higher transmission speed of 1.4Mbps. Although 128Kbps speed is more of standard in digital technology. The medium used by ISDN lines are unshielded twisted pair cables (UTP) for communication. Digital technology is international standard for communication, communication methods of sending data, voice data, video etc over digital telephones lines and these lines are ISDN lines.
Types of ISDN Network
There are two common types of ISDN networks. BRI which stands for Basic rate interface and the other type is PRI which stands for Primary rate interface. Lets these two types below.
BRI- Basic Rate Interface: It possess two 64 B-channels, 1 D-channel for controlled transmitting of information.
PRI- Primary Rate Interface: It posses 23 B-Channels and 1 D-channel for United States or 30 B-channels and 1 D-channel for European countries.
There is another version of ISDN lines, it is called B-ISDN, and it uses broadband transmission. It is used for high speed then regular ISDN lines; it can transfer data up to 1.5 Mbps. B-ISND lines require fiber optic cables. On the other hand regular ISDN lines used UTP cables and employs base band transmission.
ISDN phone line subscription requires having access to B channel ISDN network. Special ISDN devices are also required by customers, these devices are known as terminal adapters. These specific terminal devices communicate with other ISDN devices or telephone company for communication.
How ISDN Works ?
Only single transmission channel for communication is available in analog network or regular telephone lines that are provided to us by telephone companies. Therefore only one service can be carried at time, i.e. voice, data, video at single time. Whereas in ISDN lines there the same pair telephone lines are logically divided into multiple channels, they are normally divided into two channels.
B- Channel is first type of channel. 64Kbps of data can be transferred using B-channel. Normally ISDN lines possess two B channels. One channel is dedicated for voice and the other channel is dedicated for data communication. The data transmission takes place on one pair copper wire.
Second type of channel is used for line and calling system setup, is it know as D-channel or delta channel also. Third channel on the other have on 16Kpbs of bandwidt.
Advantages of ISDN lines
Speed is the most obvious advantage of ISDN line, the maximum limit for commonly used dialup connections is 56 kbps and due to many factors this limit reduce to only 45 kbps. Where as ISDN lines possess multiple digital channels which operates simultaneously by using same regular one pair copper wire. If telephone company can provide digital connections then change in speed can occur, this way digital signals can be transmitted through telephone lines rather than analogue. The digital signals can provide better transmission rates comparing analogue setup.
Multiple lines for Multiple Devices
If multiple services are required by consumer for example, fax, video conferencing, telephone etc, separate telephone line will be required for each device, where as ISDN line can handle multiple services at single line. There are eight channels which can be supported by ISDN lines simultaneously. That means one single ISDN line can support telephone, video conferencing, fax, credit card machine and other services together on single line and all these devices can work simultaneously
V.34 or V.90 modems usually takes up to 30 to 60 seconds to make connection to the network whereas ISDN lines takes less than 2 seconds to make connection live to be used.
Disadvantages of ISDN lines
There are some disadvantages associated with ISDN lines and they are as follow.
- ISDN lines are more expensive when compare to the regular landline telephone system.
- ISDN provider companies and ISDN users are require to have special dedicated line and then can encore at extra cost.
Difference between ADSL and ISDN
There are some obvious differences between the two services.
• ISDN lines provide two voice channels or one 128Kbps data channel where as ADSL is only data line, which is used for only data.
Note: Concept of ISDN line working with the help of Image.