sundance-communications.com/forum Forums General General Telephone & Systems Information how do phones actually work?

Yeah, and it would be cool to show the kids that when two phones are connected together with a line cord only, they don't work. That way, they can understand that there's something else between two phones to make a call.

Maybe that would be a good way to start the show. Plug two 2500's together and ask two kids to pick up and try to talk to each other. Then, you might have a bit more of a captive audience with your demo setup.

Hey Z,
This project looks like it could be fun, let us know what you do and how it goes.
Mark

Do not forget sound powered telephones!!

Ed it was somewhere around 1995, they knew what a 2500 set was then and some of them had the rotary in their homes, now today's kids...I couldn't say that.

Show them a bag cell phone. I used to have one. I could talk 15 minutes on the battery pack that was in it.

The bare bones basic of how a phone works . The transmitting telephone converts sound waves to electrical waves . The receiving telephone converts electrical waves back to sound waves . You can demonstrate this with 2 2500 sets , 2 line cords and a lantern battery .

The pure genius of Bell's telephone invention was that it was full duplex from inception ! Unlike telegraph , the biggest competitor at the time .

Hey, Z-Man:

I just thought of something. If you set up a simple connection with two phones and a battery, I wonder if a simple mA meter from Radio Shack in the circuit would reflect enough of a reading to show the kids how it works, like current flow when they go off-hook, how both must be off-hook before current flows, etc. Maybe the needle would bounce back and forth depending on how loud the kids speak to each other? Just a guess on that one.

I have too much time on my hands.

These kids won't understand any of that. Let's see, 6-8 years old probably? Just tell them that there is a big version of Yahoo Instant Messenger running at the phone company. They'll understand that! :toothy:

In all seriousness though, how about two simplex circuits. A microphone going to a speaker powered by a battery one way, and a duplicate going the other.

Just a thought.

Would something like this work:?

"When you talk, you produce sound waves that others can hear. As the waves travel they spread out and get weaker, which is why you can't hear people far away."

Produce a string phone:

=|-------------------|=
Can ---- string ----- Can

"The sound waves from your voice vibrate the bottom of the can, converting the sound waves into string waves. Instead of spreading out, the waves travel down the string to the other can and cause the bottom of the other can to vibrate and produce sound waves that you can hear.

"A telephone does the same thing, except it changes the sound waves into electric waves that can travel over wire.

"A cordless phone does the same, except it changes these electric waves into radio waves."

Let them keep the string phone.