Pulse amplitude modulation (PAM) is used extensively in telecommunications as an intermediate step of other techniques such as phase shift keying (PSK), quadrature amplitude modulation (QAM) and pulse code modulation (PCM) 1 . PAM however is an amplitude modulated (AM) form of a pulse carrier 2 , and hence has all the advantages and disadvantages of the purely analog AM, a major disadvantage being noise. PAM can be time-division multiplexed (TDM), as can pulse code modulation (PCM) which is a

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... gital signal. TDM is one of the multiplexing techniques used in telephony (the other is spacedivision multiplexing). PAM is used as a first step in converting voice signal to PCM in the public switched telephone network (PSTN), and is also used to produce high-level modulation schemes for data modems and digital radio. High-level modulation is done in the output circuit of the radio frequency (RF) power amplifier stage, and is more efficient than low-level modulation. PCM is used for long-distance telecommunications, making PAM an important pulse modulation technique in communications systems.