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Signals

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Everyone

Signals - Voltages, Currents or Light Pulses which Represent Information

Input transducers produce electrical currents or voltages which are proportional to a measurement of the world.

These are the useful signals. They represent ...

Music
Voice
Temperature
Light Level
Pressure
Water Level
Time of Day
Video Images
Control signals for industrial machines, vehicles and even children's toys.

Noise - Unwanted and Often Random Voltages or Currents

Noise comes from many sources ...

Industrial machinery switching on or off
Thunder storm lightning strikes ( Impulsive Noise )
Anyone using a radio transmitter
Fluorescent tubes
The background hissing noise ...
     Radio radiation from the surface of the sun
     Any warm or hot electronic component
     Carbon film resistors

Analogue Signals

Analogue signals have an infinite range of values between a minimum and a maximum.
Analogue signals are processed using Comparators and Amplifiers.
Analogue signals are usually smoothly varying - there are exceptions like lightning strikes

Digital Signals

Digital signals have exactly two values - ON or OFF
Digital signals are mostly processed using LOGIC CIRCUITS
Digital signals have the typical square wave shape.

D to A and A to D Converters

A to D: It's possible to convert analogue signals into digital. The simplest converter is a Comparator. To record voice or music onto a phone, iPod or similar computing device, the analogue signal must be converted into digital.

D to A: It's possible to convert digital signals into analogue. To play music from a phone, iPod or similar device, digital data is first converted into analogue.