What are the physics of a telephone?

Answer 1

Speaker's Vocal Chords ===

• The person speaking into the phone passes air by their vocal chords making a basic tone, the mouth then shapes the tones into words. Audible Sound Waves are produced that propogate toward the phones microphone.

Microphone / Transducer

• The microphone or transducer will respond to the sound waves and convert mechanical energy into electical energy. This is typically through the reverse mechanices of a speaker. In this case, the cone shaped "floating" mechanical piece reacts to the sound waves of the person speaking into the phone. This creates an oscillating motion that moves a electrical coil around a magnetic field. This produces oscillating electrical voltage/current in proportion to the speed that the microphone oscillates. At the output of the microphone is a sinusoidal electrical wave form.

Analog to Digital Converter (A-D Converter)

• The analog electrical signal has to be digitized so that we can take advantage of computer processing in the transmission. An Analog to Digital Converter is used.

Compression Algorithms

• Sending the entire raw signal takes too long. The signal is passed through a modified Fast Fourier Transform FFT routine to come up with the basic waveform coefficients.

Transmission

• Analog or Digital communication

  with Digital you can have Spread Spectrum and increased security.

Reciever

• The person being called picks up their receiver when their phone rings and the process reverses itself.

DecoderDigital to Analog Converter (D-A Converter)

Telephone Speaker

Answer 2

Boiled down, the telephone can do two things simultaneously:

(1) Convert speech (sound waves) into an electrical signal than can travel through wires.

(2) Convert that electrical signal back into audible sound waves.

The first component is a microphone in the mouthpiece.

The second component is a speaker in the earpiece.

Both are examples of transducers -- devices that convert electrical energy to/from mechanical energy.

Alexander Graham Bell figured out how to make both kinds of transducers.

Then he connected two sets by long wires and applied a DC voltage from a battery. Modern telephones (land lines) still do pretty much the same thing.

Answer 3

The science behind the discovery is physics and electronics because of the sound waves that pass through the telephone to the electrical wire and to another telephone.