Analog signal	Digital signal
1. Analog signal is a continuous electromagnetic waves that may be propagated in a media depending on frequency. 2. For example : Copper wire media, such as Twisted pair and Coaxial cable, Fiber optic cable and atmosphere or space propagation ( wireless ). 3. Analog data can be represented by digital signals . 4. Analog data are encoded to occupy a different portion of spectrum .	1. Digital signal is a sequence of voltage pulses that may be transmitted over copper wire medium. 2. For example : A constant positive voltage level may represent binary 1 and a constant negative voltage level may represent binary 0 . 3. Digital data can be represented directly, in binary form, by two voltage levels. 4. Analog data are encoded using a codec to produce a digital bit stream.

Analog signal converted into Digital signal : Analog signal is converted into Digital signal by either of two methods:

1. PCM ( Pulse code Modulation )

2. Delta Modulation ( DM )

PCM is based on Sampling theorem whereas DM is binary behavior .