• Analog voice data must be translated into a series of binary digits before they can be transmitted in
digital transmission system. One means of doing this is called pulse amplitude modulation (PAM).
• The process of converting analog signal to digital is also known as A_to_D conversion or A/D
conversion. The circuit does the conversion known as A/D converter.
In analog modulation (continuous wave modulation), some parameter of a sinusoidal carrier wave is
varied continuously in accordance with the message signal.