How do you make a phone?

Question

How do you make a phone?

Answer 1

Please see link below for building a telephone.

Answer 2

Let me try three answers and see if I get close to what you want to know.  

1.  Two tin cans and a string.  It really works, just keep the string tight.

2.  If you want an electrical phone, you need a way to 'transduce' electrical signals into sound so you can hear, and a way to do the reverse--convert sound vibrations into electrical signals, or variations in electrical signals.  The basic idea here is that the phone company (with traditional land-line phones) provides a DC signal that starts out at 48v DC, and drops some voltage over the phone lines.  If you couple a speaker and a little amplifier to that DC line with a capacitor, you will get some sound.  If you design the interface carefully, you'll get better sound.  Actual phones have a 'hybrid' circuit that breaks the transmit and receive signals into seperate paths as much as possible, to avoid feedback and limit the signal you get in your ear when you talk, leaving a little bit, which sometimes is referred to as 'sidetone', but I digress.  The traditional way to convert sound waves INTO electical waveforms is with a carbon button microphone, which can best be found by unscrewing the mouthpiece from a 1950-80 vintage telephone.  If there is a round cartridge thing that falls out, it's probably a carbon button mic.  When you talk into the microphone, it varies the resistance of the cartridge, and so increases and decreases the current through the phone circuit in a manner more or less proporational to your speech, so the person on the other end of the call can hear you.   If you had two simple phones, you could connect them together with a large battery and talk over a single pair of wires.  If you want to dial the phone, you would probably want to either add a touch tone pad, which generates the appropriate dialing tones, and must be coupled to the transmit audio path, or a dial might still work in some situations, which interrupts the phone circuit once for each digit, i.e., it clicks the line three times to dial a '3', five times to dial a '5', and ten times to dial a 'zero'.  Eleven pulses is often interpreted as a star key, maybe twelve would look like a #, I'm not sure.  

3.  The third answer is that if you have a design in mind for a phone (and if that's the case I probably should have made this answer number 2), there are a number of design/fab/prototype firms out there that will build a manufacturing prototype, or you could build one yourself and save a ton of money.  There are contract manufacturers who can help setting up molds, PC etching, and manufacturing, but it will require a pretty large bankroll to start, and then you need marketing channels, FCC type approval for sale in the US, and a few other things, most of which are surmountable, though large obstacles.

I don't know if this was any help at all, but it was fun to think about it!