modulate

1. Change or vary in some way. 2. In acoustics, modulation involves varying the pitch, tone, or volume of an audio signal, such as the human voice. 3. In physics, modulation involves varying the characteristics of an electromagnetic waveform, generally by varying the amplitude, frequency, or phase, or some combination. 4. In telecommunications, modems perform signal modulation and demodulation processes to encode information from digital devices onto signals carried by analog circuits. Digital Service Units (DSUs) and various other devices modulate carrier waves to place digital signals on digital circuits. See also AM, FM, modem, PM, and PSK. 5. In telecommunications, codecs code analog signals into digital format prior to transmission over a digital circuit, and decode them on the receiving end of the connection. Codecs use a variety of modulation techniques, including adaptive differential pulse code modulation (ADPCM), differential pulse code modulation (DPCM), and pulse code modulation (PCM).

See also ADPCM, analog, codec, digital, DPCM, and PCM.

• Narrowband AMPS (N-AMPS)
• Narrowband ISDN (N-ISDN)
• Narrowband PCS (Narrowband Personal Communications Services or N-PCS)
• Narrowband TACS (NTACS)
• Narrowband Total Access Communications System (NTACS)
• narrowcast
• NAS
• NA-TDMA (North American Time Division Multiple Access)
• National Bureau of Standards (NBS)
• National Do-Not-Call Registry
• National Electrical Code (NEC)
• National Exchange Carrier Association (NECA)
• National Information Infrastructure (NII)
• National Institute of Standards and Technology (NIST)
• National Internet Registry (NIR)
• nationalize
• National Research and Education Network (NREN)
• National Science Foundation (NSF)
• National Television Standards Committee (NTSC)
• native
• NAT (Network Address Translation)
• natural monopoly
• NBS (National Bureau of Standards)
• NCC (Network Control Center)
• NCP