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The ISDN telephone line is terminated on a common box called the network termination (NT) at the subscriber premises. Beyond this box, on the internal wiring in the subscriber's premises, up to 8 ISDN terminals can be connected. These ISDN terminals can be of several types, for example , ISDN telephone, personal computer (PC), video phone, video conferencing equipment , G-4 Fax machine Etc. in addition the existing terminals such as rotary & push button telephone, G-3 fax machines and modems can also be connected to the internal wiring with suitable interface called terminal adaptor (TA).
The network termination unit along with 4 sockets will be provided by MTNL or can be provided by the subscriber at his choice. The terminal equipment has to be procured by the subscriber himself from the open market. Only the DOT's type interface approved terminal equipments can be connected to ISDN line. Details of some of the ISDN terminals are given below :
Simple ISDN Handset : It is the simplest type of ISDN terminal and consists of a had set and a phone unit. The telephone converts the user's speech in to digital form for communication on ISDN line.
ISDN Feature Phone : This terminals, in addition to having a handset and dialling key pad, also has a LCD display , additional keys for storing frequently dialled numbers & other function keys.
1) DISPLAY :
The ISDN phone has an LDC display resembling those available in calculators. Caller can leisurely enter the digits to be dialled ( which are displayed) since the actual dialling does not take place as you press the digits but by an explicit action , say,lifting the hand set etc.This reduces wrong calling. In case of CLIP service the calling number of call units charged is displayed. This is also used for programming of MSN, CF etc. This combined with speaker phone facility true hands free operation.
2) LOGGING :
The logging facility provides for automatic storing of calling subscriber number, when the call could not be answered . The calling number can be recalled using the log. Other facilities like redialling, memory dialling and speaker phone are also available. The phone is also called a digital phone, since signals are transmitted and received in digital form. So the phone provides clear and noise free conversation. In ISDN, the line condition is always checked continuously , so that any fault in the line is immediately detected.
Terminal Adaptor : The existing terminals like rotary telephone, push button telephone, personal computer , G-3 fax machine etc. can be connected to the ISDN line through a terminal adaptor (TA). The terminal adaptor provides connectivity to ISDN line on one side. On the other side a number of connections are possible to which various types of existing equipment described above can be connected.
1) Analogue Connector :
Rotary telephones, push button telephones (pulse type or tone type), fax, answering machines, cordless phones etc. can be connected to this port /connector.
2) Data Port :
Any PC with Rs 232C connection ( serial port of the PC) can be connected to this port, Data transfer using standard software packages like X talk or procomm is possible up to 9.6 Kbps. Modem is not required.
PC Add -on ISDN Card : This card can be fitted in standard personal computers and can be used for data transfer at 64 kbps. This card fits into vacant slot of any standard 386 /- 486 PC etc. A software is also provided which will be installed in the PC. A connector on the Pc provides the interconnection to the ISDN line. Files from the PC can be transmitted or received at the speed of 64 Kbps. At this speed , the complete information on a 2 Mbyte floppy can be transmitted in 4 minutes. Using both the channels it is possible to send the data at 128 kbps.
Video Conferencing Equipment : This equipment consists of a computer , TV monitor, camera and other control units. This is a professional equipment and will be connected to the network using 3 ISDN lines. The equipment establishes connection to a similar equipment on the other side by dialling through the network. Moving video images of the conference participants can be sent as well as received along with their conversation. It is possible to send diagrams and photographs by a still picture camera . Data transfer can also be done simultaneously . The equipment works at 384 Kbps. In addition, video images can be sent or received on auxiliary equipment like VCR.
Using the control panel, the video camera can be moved or zoomed on the required participants of the conference. The transmitted picture can be viewed along with the received picture.
Video Phone : This is a compact version of the video conferencing equipment. The equipment consists of a compact screen with a camera . This requires only one ISDN line. Video images and conversation are sent and received at 128 kbps. This could also be available as an 'add on'facility on a PC.
For List of T.E.C. approved ISDN terminals, click here
Last updated on 17.06.2010
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