The Difference Between Analog and Digital Signals

Analog Signals

Analog signals are a representation of time varying in a continuous signal.Analog signals are required to represent real world signal.Analog signals work with natural phenomena and physical values like frequency, earthquake and volcano, flow of water, speed of wind, weight, lighting and many others.The characteristic of an analog signal include following:

• The signal is continuously variable in both amplitude and frequency.
• The traffic measurement is Hertz (Hz) (for example, a telephone channel is 4(kilohertz)KHZ)
• It has a low bandwidth (4 KHz), which means low data transmission rates (upto33.6Kbps) because of limited channel bandwidth.
• It has a low network conversation per telephone channel.
• Analog signal have a poor network manageability. A lot of labor is needed for the network maintenance and control because dumb analog devices do not provide management information streams that allow the device to be remotely managed.
• It has a high power requirement because signal contains a wide range of frequencies and amplitudes.
• It has got a poor security. When you tap into an analog circuit, you hear the voice stream in its native form and it is difficult to detect an intrusion.
• Analog signals have high error rates.10-5 bits (that is, 1 in 100,000bits) is not guaranteed to have an error.

Digital signal are signals with discrete set of values.Digital signal are also a series of ONs and OFFs (represented by 1s and 0s).these can be voltages going from a high(one)value to a low (zero) value or flashes of light.it is usually encoded into binary in order to carry out information.The characteristics of digital signals include the following;

• It has a good security for example; encryption can be used.
• The power requirement is low because only two discrete signals-the one and the zero need to be transmitted.,
• Digital signals have high band width that can support high speed data and emerging applications that involve video and multimedia.
• It has a high network capacity. Multiplexers enable conversations to share a communications channel and hence to achieve greater transmission efficiencies.
• It has a good network manageability; smart devices produce alerts, alarms, traffic statistics and performance measurements and technicians at a network control center or network operations center can remotely monitor and manage the various network elements.
• Digital signals present data in a discrete signal represented as either changes in voltage or changes in light levels.• Its traffic measurement is in Bits per second (for example a T-1line carries 1.544Mbps and E-1 line transports 2.048Mbps)
• It has a low error rates

Benefits of converting an analog voice signal into a digital voice signal includes the following:

• Analog signal facilities have limited band width which means they cannot support high-speed data while digital signal facilities allow high-speed data because they have a wide range of bandwidth.
• Digital signal does not get noise interference as data is being transmitted and the regenerative repeaters eliminates the noise by converting the signals to strictly ones and zeros thus eliminating the noise. But, analog signal accumulates noise as the signal traverses the network.
• In digital signal there are low error rates other than in an analog signal where the signal is mixed with noise which makes it hard to determine the right signal which cause very many errors.
• It is easier to reproduce digital signals using the regenerative repeater which converts the signal back into ones and zeros unlike in an analog signal where the signal is passed through the amplifier which does not sort out the noise from the signal making the reproduction of the signal difficult.
• Digital signal have a high network capacity that enables it to transport the signal smoothly unlike an analog signal which has limited network capacity.

How analog signals are connected from a transmitter to a receiverWhen it comes to an analog circuit-what we refer to as a voice-grade-line we need to also define the frequency band in which it operates. The human voice for example can typically generate frequencies from 100Hz to 10,000Hz, for a bandwidth of 9,900Hz.But the ear does not require a vast range of frequencies to elicit meaning from ordinary speech; the vast majority of sounds we make that constitute the intelligible speech fall between 250Hz and 3,400Hz.So, the phone company typically allotted a total bandwidth of 4,000Hz for voice transmission.

Remember that the total frequency spectrum of twisted-pair is 1MHz.to provision a voice-grade analog circuit, bandwidth-limiting filters are put on that circuit to filter out all frequencies above 4,000Hz.That’s why analog facility is 33.6Kps when there are analog loops at either end.How the 56Kps modems break the 33.6Kps BarrierWith 56Kps modems, only one end of the loop can be analog. The other end of the connection has to be digital. , in other words, if you are using a 56Kps modem to access your internet service provider (ISP), you have an analog connection from your home to the local exchange. But the ISP has a digital termination facility from its location to its exchange.How digital signals are coupled from a coder to a decoder.How the ones and zeros are physically carried through the network depends on whether the network is electrical or optical.In electrical networks, one bits are represented as high voltage, and zero bits are represented as null, or low voltage.In optical networks, one bits are represented by the presence of light and the zero bit are represented by the absence of light.The ones and zeros-on/off conditions are carried through the network and the receiving device repackages the ones and zeros to determine what character is being represented. Because a digital signal is easier to reproduce than an analog signal, we can treat it with less care in the network. Rather than use dumb amplifiers, digital networks use regenerative repeaters, also referred to signal regenerators. As a strong, clean, digital pulse travels over a distance, it loses power, similar to an analog signal.

The digital pulse, like an analog signal is eroded by impairments in the network .but the weakened and impaired signal enters the regenerative repeater, where the repeater examines the signal to determine what was supposed to be one and what was supposed to be a zero. The repeater regenerates a new signal to pass on the next point in the network, in essence eliminating noise and thus vastly improving error rate.