This instructable will progressively show how to make at least one kind of telephone that sounds good enough to be fun and useful, without requiring batteries, AC utility company power, or utility telephone services.
I suppose it may be most appreciated by smart young children with "forts".
Step 1: Things you will need
Since I have done this before I know that the following supplies will be needed:
Two SMALL transistor radio speakers with BIG MAGNETS. Usually they are 8 ohms,
... higher resistance would be better, they could be (rare) 16, 32, 45, 100, or 600 ohms
as long as they are both the same ohms resistance.
The speaker size is almost perfect if both of them can hide under a CD. Bigger is not better.
Wire... Telephone wire or computer network wire or extension cord wire WITHOUT PLUGS.
Optional but very effective... some things like horns or cones.
I suppose you could use cans instead of horns.
But I'll try to show how to make a horn like those ancient wind up groovy-disc music boxes have.
Optional for long distance... high impedance matching transformer such as used in PA systems,
or which are designed for tube or transistor radios to match 8 ohm speakers to 1,000 or 10,000 ohm
amplifiers. Such transformers are also used in some speakers in systems for playing
background music and paging in supermarkets.
Distance is limited by how much wire you have and how far you can run it without annoying anyone,
especially the police.
You don't need all this stuff. Just one long pair of wire and two speakers will be enough.