Amplifier -telephone connection

Woody60

(not sure if I'm in the right forum here - but perhaps someone can redirect me if not).
This is the problem I have:
I am trying to link in a telephone line to an amplifier. The amplifier is used in a meeting hall that has wirelss microphones and we want to be able to phone in to a conferencing system so that those unable to be present can listen to what goes on.
I have the telphone line but am stuck on what interface to use to the amplifier.
Any ideas please?

FusionNet

Have you got a telephone system in place already, and if so what brand and model is it? How many callers would you like to be able to dial in? Is it only one way you want the system to work and in the callers will not be able to converse also?

Woody60

We have just an Eircom line coming in to the building but no telephone yet (depends on replies to this post)

There would probably be a maximum 5-10 people at any one time.
Would be good if they could participate but not essential.
There will be a participatory meeting going on which we want them to be able to listen to, and the opportunity to participate would be welcomed.
Thanks

Fuzzy Clam

You could do it with a telephone hybrid as used by broadcast stations to put callers on air.
The phone line is plugged directly into the hybrid and an audio cable goes to the amp so the caller can be heard over the amp. A second cable goes from the amp "aux send" to the hybrid so the caller can hear the meeting.
If its not possible to wire it in that way with the amp you have (it may not have aux sends), then a small mixing desk may be needed.

As to how to get 5 or 10 calls on at the same time, I'm not sure.

There may be another way of doing it using broadband and a laptop with Skype.

FusionNet

It could be donr using a quality PBX but one line wont do. You'd need multiple ISDN's to handle it.. Have you got budgets for such things?

Woody60

Actually the multiple lines bit isn't a problem. I will use a service called AllConferenceCalls.com which enables all parties to call in to a central number with a pin code.
It's just the technical bit of getting the amp output down the telephone line.
These hybrid units are not cheap, so was wondering if there was a simpler (=cheaper) way of doing it.

Fuzzy Clam

I'm sure you can get a hybrid for around 100 E. BTS in Bluebell, Dublin do them although you may need to go through Audiocity (www.audiocity.ie) to deal with them as they are trade.
The cheapest way to do it would be to use a 600 ohm 1:1 transformer wired between the line level output of the the amp and the phone line. Radionics do these. This will allow only one way speech though.
Its certainly easy enough for a competent person to make a hybrid cheaply to allow 2 way.

Woody60

Great suggestion. Thanks a million