Pulse amplitude modulation (PAM)

The most common and most important method that a telephone system in North America can use to sample a voice signal and convert that sample into an equivalent digital code. PCM is a digital modulation method that encodes a pulse amplitude modulated signal into a PCM signal.
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A piece of equipment that joins a digital phone line to a piece of communication equipment, which may be a phone or a PC. Such equipment allows testing, condition, timing, interfacing, etc. However, it does not do what a modem does: namely, convert digital signals from machines into analog signals which can be carried on analog phone lines. The term “digital modem” is thus somewhat of a misnomer.
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The technique of varying the amplitude or wavelength of a carrier wave in direct proportion to the strength of the input signal while maintaining a constant frequency and phase.
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A modulation technique in which the carrier frequency is shifted by an amount proportional to the value of the modulating signal. The amplitude of the carrier signal remains constant. The information signal causes the carrier signal to increase or decrease its frequency based on the waveform of the information signal.
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A piece of hardware used to connect computers (or certain other network devices) together via a serial cable (usually a telephone line). When data is sent from your computer, the modem takes the digital data and converts it to an analog signal (the modulator portion). When you receive data into your computer via modem, the modem takes the analog signal and converts it to a digital signal that your computer will understand (the demodulator portion).
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