Analog signals (technologies)
Analog signals are continuous signals that can vary in amplitude, frequency, or both, allowing for an infinite range of values. Unlike digital signals, which are limited to discrete values (essentially represented as on or off), analog signals can provide a denser and richer experience, often appreciated in applications like music recording and transmission. For instance, early analog sound recordings utilized grooves on records, while magnetic tapes recorded audio as magnetic impulses. However, analog signals are susceptible to degradation over time, particularly as they are played back or amplified, leading to increased background noise that can distort the original signal.
While analog technology has benefits, such as capturing the full tonal qualities of sound, it presents challenges in modern telecommunications. Analog signals occupy more network capacity and require more power to transmit than their digital counterparts, which can transmit multiple signals simultaneously and with greater efficiency. Digital signals are also more secure and can travel faster, making them better suited for high-speed data communication. Despite the prevalence of digital technology, many devices still rely on analog signals for input, necessitating the use of analog-to-digital converters for seamless integration between the two forms. Understanding the strengths and limitations of analog signals is essential for anyone exploring the landscape of audio technology and telecommunications.
On this Page
Subject Terms
Analog signals (technologies)
A signal is a physical quantity that delivers information. An analog signal has an infinite range while a digital signal has a limited, defined range. To illustrate the difference, imagine two clocks. An analog clock has hands that move continuously and smoothly and can show all units of time (hours, minutes, and seconds). A digital clock, on the hand, can only show the units of time its display allows for, usually just hours and minutes. Analog signals are continuous, while digital signals are simple pulses: they are either on or off.
Overview
Analog signals are much denser than digital signals and contain much more information. However, noise and interference can diminish the sound quality, especially when a signal is copied repeatedly. Music is one type of signal that is commonly recorded and transmitted. Early analog sound recordings consisted of grooves on records. Tapes recorded analog data as magnetic impulses. The recordings are read by a device that makes contact with the groove or magnetic impulse. Because these recordings come into contact with a record player needle or a tape player head, they degrade, or lose quality, a little bit each time they are played. This change is so slight that it may not be perceptible for some time, but degradation is inevitable.
Analog signals are also altered when they are amplified, or made louder by increasing their strength. Analog signals will pick up random extra signals as they travel. This noise is amplified along with the intended transmission and increases with every amplification. In time, the background noise may overwhelm a broadcast, such as when a radio transmission becomes overrun by static. The intended signal eventually becomes indistinguishable from the noise because the amplifier simply boosts the signal and cannot interpret the data. Digital signals, too, can erode during transmission, becoming weaker and degrading due to issues such as a damp cable. However, these signals are amplified by regenerative repeaters, which are not dumb amplifiers. The regenerative repeater examines the signal, discards the noise, and regenerates the signal to forward to the next point in the network.
Analog signals can vary in amplitude, frequency, or both. For example, AM radio is amplitude-modulated radio while FM radio is frequency-modulated radio. Signals may pass through wires or similar means or through the air.
When analog signals are converted to digital, such as to make copies, the signal is broken into pieces. These bits may be extremely small and close together—a dense signal—but they cannot be continuous and will never approach the density of the analog signal. A high-quality digital signal will sound clear and continuous. Some music purists, however, insist that analog recordings deliver a better sound because they include infinite tonal qualities.
Analog signals are a disadvantage in cell phone transmissions. Cell phones translate the human voice, which is infinitely variable, into digital signals. The human voice can range to frequencies of 10,000Hz, but the majority of speech sounds are from 250Hz to 3,400Hz. Phone companies generally limit voice transmission to a bandwidth of 4,000Hz. The human ear does not require the complete range of signals to comprehend speech, so digital transmissions are easily understood even within this severely limited bandwidth. The network capacity for an analog signal is low, so only one phone conversation can occupy a telephone channel while multiple digital signals can share one communication channel and be transmitted more efficiently.
Analog signals require a great deal of power to transmit the wide-ranging amplitudes and frequencies. Digital signals, on the other hand, are transmitting pulses—the one and the zero, on and off—so they use very little power in comparison.
Digital signals also travel more quickly than analog signals, so analog is generally used for low-speed data communication. This difference also explains the necessity of using digital signals with modems to connect to the Internet for high-speed transmissions. Another advantage of digital signals is security. An analog transmission cannot be encrypted and is likely to be insecure. An intrusion on an analog transmission may be difficult to detect.
Though modern computers are generally digital, many of the signals they receive, such as heat, light, and sound, are analog. Consumer products we regard as digital, including thermometers, cell phones, and appliances, have analog integrated circuits, which are considerably more complicated to design than digital circuits. Pioneers of analog integrated circuits and amplifiers include the team of Robert Widlar and Dave Talbert; Hans Camenzind; David Fullagar; Robert Dobkin; Barrie Gilbert; and Paul Brokaw.
Analog and digital components are frequently integrated in a circuit. Analog-to-digital converters, for example, are quite common. These permit microcontrollers to connect to analog sensors, such as photocells. Conversion of a signal from analog to digital is the point at which network problems are likely to take place. For this reason, efforts are being made to develop transmissions that are completely digital, from start to finish, without requiring conversion.
Bibliography
"Analog and Digital Signals." All About Circuits. All About Circuits. Web. 7 Nov. 2014. <http://www.allaboutcircuits.com/vol‗1/chpt‗9/1.html>
"Analog Integrated Circuits." Exhibition: Digital Logic. Computer History Museum. Web. 10 Nov. 2014. <http://www.computerhistory.org/revolution/digital-logic/12/281>
"Data Transmission." Bitesize. BBC. Web. 7 Nov. 2014. <http://www.bbc.co.uk/schools/gcsebitesize/science/ocr‗gateway/home‗energy/data‗transmissionrev1.shtml>
Goleniewski, Lillian. "Telecommunications Technology Fundamentals." Informit. Pearson Education, Informit. 28 Dec. 2001. Web. 10 Nov. 2014. <http://www.informit.com/articles/article.aspx?p=24687&seqNum=5>
Jimbo. "Analog vs. Digital." Tutorials. SparkFun Electronics. Web. 7 Nov. 2014. <https://learn.sparkfun.com/tutorials/analog-vs-digital/all>
Maiklem, Lara (ed.). Ultimate Visual Dictionary of Science. New York: Barnes & Noble Publishing, 2006. 350 – 355.
"Sending Information." Bitesize. BBC. Web. 7 Nov. 2014. <http://www.bbc.co.uk/schools/gcsebitesize/science/aqa‗pre‗2011/radiation/sendingrev2.shtml>
"Waves and Communication." Bitesize. BBC. Web. 7 Nov. 2014. <http://www.bbc.co.uk/schools/gcsebitesize/science/21c/radiation‗life/waves‗communicationrev2.shtml>
"What Is an Analog Signal?." WiseGeek. Conjecture Corporation. Web. 7 Nov. 2014. <http://www.wisegeek.org/what-is-an-analog-signal.htm>
Williams, Ryan C. "Understanding Digital Sound and Analog Sound." For Dummies. John Wiley & Sons, Inc. Web. 7 Nov. 2014. <http://www.dummies.com/how-to/content/understanding-digital-sound-and-analog-sound.html>