Help with design

Hi, Please excuse the extreme ignorance of the question I am about to pose. I am fairly handy, but have little in the way of electronics know-how.

A friend of mine is a children's speech therapist who recently had her therapy room remodeled. There is a need for the parents who are observing their children to be able to hear the therapy session. The parents are outside of the room observing through a one-way mirror. No one else should be able to hear what is going on in the room (wireless systems that could be 'overheard' would not be acceptable). Any equipment in the room should be silent and unobtrusive so as not to disturb the session.

One idea we had is to have a microphone put in a wall with a grill over it. From the outside, the parents could perhaps plug headphones into some kind of jack in the outer wall. Does this sound feasible? What would it take to make this system work? I presume the microphone would be attached to an amplifier and that would be wired to the jack.

Any other suggestions? If you could be as specific as you can with model numbers and suppliers that would be great.

Thanks for your help and suggestions.

-g

Reply to
gyro
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Your suggestion is probably the simplest and cheapest to get working but it might be worth putting the microphone in the center of the room or have several sockets into which movable microphones could be plugged on cables.

Try speaking to the sound engineer at your local theater or to a company that installs PA systems and the like.

For info a wireless solution need not be unsecure - it's all a matter of degree. Wired systems can be "tapped" and the system you propose dosen't encrypt the data so a tap would be all you need. It's possible to do voice over IP using palmtop computers and wireless LAN cards with a reasonable level of security (eg basic encryption) but you would need to do some research.

This web site might be worth a read (perhaps skip the first paragraph or two).

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Reply to
CWatters

Thank you for the suggestions. A moveable microphone would be good if it could be made unobtrusive

I should have mentioned that the solution should be low cost, as this is a not-for-profit agency. Many of the renovations being put in place are being done by family and friends.

The issue of 'tapping' isn't a big one. I just want to make sure that people with a scanner or walkie talkie (or baby monitor) can't tune in to the therapy session. The people that work at the agency are therapists, not computer/electronic experts, so the system should be as foolproof and maintenance-free as possible.

Any ideas where one can buy the necessary parts for a simple system?

-g

Reply to
gyro

Do their telephones have intercom built in? If so, all you need is a couple telephones. One in the therapy room with the handset laying on the desk or table, and another to listen to that phone.

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Reply to
Michael A. Terrell

Thanks for the interesting idea. They seem to have a shortage of most of the electronic conveniences, but I'll certainly check.

The clients (most of whom are autistic or have other developmental delays) may have a problem concentrating if there is some unusual 'prop' in the setting.

-g

Reply to
gyro

As small as microphones are being made these days (tie-clip mic, cell phone headsets), this should be duck soup. The hardest part is hiding the wire. Any amplifier and speaker you can get should complete the package. Even Radio Shack can do this.

Reply to
JeffM

You can build a simple telephone intercom with a well filtered 24 volt DC power supply, and an audio choke. Parallel the phones, and connect the choke in one of the lines to the power supply. Old Western Electric, or Stromberg Carlson 500 series phones work great, and can be found for nothing.

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Reply to
Michael A. Terrell

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