Definition of signal in The Network Encyclopedia.

What is Signal?

An electrical transmission of alternating current (AC) on network cabling that is generated by a networking component such as a network interface card (NIC). Signals are purposeful transmissions, as opposed to noise, which is an undesirable transmission from other components or the environment.

In the networking environment, all electrical signals are digital except when the following devices are used:

  • Modems:
    Convert the digital signal from the serial port of a computer to an analog signal for transmission as audible sound waves over a phone line


  • Digital cellular phones:
    Convert the analog signal of sound waves produced by human speech into digital electrical pulses by sampling the sound wave at discrete intervals


Digital signals are essentially square waves, but they must also be encoded using line code, which represents binary information using discrete voltages.