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Joined: 03-Mar-2012
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Quote siba007 Replybullet Topic: Live Audio Conferencing
    Posted: 03-Mar-2012 at 9:36pm
sir please give some idea about live audio conferencing project.i hv no idea about this and i m not gating information about this topic from internet pleaseeeeeeeeeeeee

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Quote skumar Replybullet Posted: 17-Mar-2012 at 10:36pm
Audio Conferencing
Audio conferencing is concerned with two-way voice communication among multiple locations in real time. This generally operates through the public telephone networks. At the simplest, audio conferencing can be among 3 or 4 different locations through the normal telephone instruments. Sometimes, audio conferencing through the public radio network, using phone – in facilities can be used.

Individual microphones for the participants and external speakers at each location are employed in professional systems to carry out the conferences in a hands-free manner. Such systems can also enable a group of people to participate from each of the locations, rather than single individuals.

Audio conferences are routine phenomena in the corporate world. Countries like Australia, New Zealand, Canada and India where populations are widely dispersed have successfully used this technology in education as well.

The technical system of a typical audio conferencing network invariably consists of an Audio Bridge. This device is somewhat similar to an EPABX board at which a number of telephone lines are terminated. Telephone calls can be received at or sent out from the bridge and all the lines can be combined such that the callers can simultaneously talk among themselves as if in a conference. There can be as many participating locations in an audio conference as the number of telephone lines that the bridge can handle.

Professional quality audio conferencing systems also incorporate the following features:
􀅆 Acoustic treatment for the conference rooms for better clarity of speech and to reduce sound disturbances from outside.
􀅆 Use of leased lines or ISDN in place of normal telephone lines.

Basically, there are two different ways in which the audio conferencing takes place:
􀅆 ‘Dial-up’ Mode
􀅆 ‘Meet-me’ Mode

‘Dial-up’ Mode:
In this mode, the bridge operator initiates the calls to the individual locations one by one and initiates the conference mode after completing the dial-up process.

In case the number of locations involved exceeds five or so, this mode consumes a lot of time in setting up the conference and so the ‘Meet-me’ mode is preferred.

‘Meet-me’ Mode
In this mode, the different locations are expected to dial-in to the audio bridge on the designated telephone numbers at the appointed time of the conference. The operator at the bridge receives each of these calls and puts them on hold. Once all participants have called-in, the operator initiates the conference mode and the conference begins. The switching mechanism at the bridge also provides for late callers to be admitted into the conference.

The disadvantage is that all the locations should have the means for making long distance calls and also that a better sense of punctuality is needed on their part to call in exactly at the right time. Holding time for the callers is more and that can prove expensive.

Normal telephone conversations take place in the so-called half-duplex mode, i.e, the same pair of lines is used for talking as well as for listening. Half-duplex network causes noise buildup on conference systems, especially where many locations are involved.

Dedicated lines employing the full-duplex mode, i.e, separate pair of lines for talking and listening or ISDN links can avoid this problem and a more natural flow of two-way conversations.

For the best available options, the local telephone service provider may be consulted.

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Quote skumar Replybullet Posted: 17-Mar-2012 at 10:40pm
Audio-graphic Conferencing

In audio-graphic conferencing, static visuals like graphics, charts, pictures, photographs, etc can also be exchanged through the same communication links, in addition to audio. In more sophisticated versions of audio-graphic conferencing slow-scan video images, such as of the participants themselves, can also be exchanged.

Teaching End : Some of the more common visual enhancement technologies used in audio-graphic conferencing systems are:
􀅆 Facsimile systems: for sending pages of scanned print material for the learners to receive paper copies.
􀅆 Tele-writing devices: for writing that could be transmitted and projected in the learner centers on an overhead projector/TV monitor
􀅆 Slide-projectors/microfiche
􀅆 Slow-scan TV Systems (SSTV)

SSTV is a particularly useful value addition. The hardware at the teaching end basically consists of conventional Closed Circuit Television (CCTV) cameras, monitors and other accessories along with ‘scan conversion’ devices, which reduce the bandwidth of the visual signals from the original 5 MHz to around 1 KHz, so that the same can be sent out on voice-grade circuits.

Multiple cameras can be used e.g. one camera with freeze frame for shooting the participants, a second one to shoot flip charts, etc and a third one mounted on a caption stand to view pre-prepared graphics, maps, etc. Other sources like power point slides on a computer and video cassettes play back can also be integrated with SSTV. The images can also be recorded on a VCR for later use.

Learner Centres : A similar scan converter is required at the receiving/learner centers to reconstruct the video signals to standard TV format.
The learner centers can have a variety of display options ranging from small portable video monitors placed individually in front of the learners or a bigger monitor for group viewing, or a projection TV on wide-screen for much larger gatherings.
The learner centers can interact with the teaching end through audio only or by using a combination of telephone and other technologies such as e-mail, fax, etc to move both voice and visual information to different centres.

For situations where most visual requirements in an educational context can be met through still graphics and images, audio-graphic conferencing can be as effective as video conferencing. It proves cost-effective as only telephone lines are used for carrying voice and visual signals. However, the quality of visuals may not be that good.
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