Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

An analog signal is a form of propagated energy, such as a sound wave, that vibrates the medium it travels through. Sound waves are measured by their frequency in cycles per second, or hertz (Hz). Digital signals are transmitted over media by representing the binary digits as electrical pulses in which each pulse is a signal element. The voltage of the line is varied between a high state and a low state. For example, a binary 1 may be transmitted by applying a high voltage and binary 0 may be transmitted by applying a low voltage. Bandwidth is a term that refers to the number of bits per second that can be transmitted over a link.

This topic continues in "The Encyclopedia of Networking and Telecommunications" with a discussion of the following:

• Analog and digital signals
• Electrical and optical signaling
• Signal degradations
• Signal encoding schemes, including:
• Unipolar
• Bipolar
• RZ (return to zero)
• NRZI (nonreturn to zero, invert on ones)
• Manchester

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