Communications: Digital or Analogue

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
There are two different ways of sending information using signals. These are called and digital signals.

An example of analogue information when music is recorded onto tape.


To record live music, a is used to convert the sound into an electrical signal. The electrical signal is then stored as information on the magnetic tape. Unlike digital signals the analogue signal change from one value to the next.

A certain amount of unwanted signal is always present in a tape recording. This is known as . When the tape is played back, the analogue signal is converted into music through . The noise of often detected as in the backgound. Circuitry such as Noise Reduction can help to reduce this unwanted signal.

Digital signals only have two states. These are known as 0 or 1. An analogue signal can be changed into a digital signal by using an to digital converter . To record music onto a compact disc it is necessary to use a converter. This changes the continuously changing music signal into binary . The circuitry takes of the original analogue signal. Each binary number is stored as a of 16 bits. The sampling process happens at 44100 times a .

Some information is always when converting from analogue to digital signals. This is why the sampling rate is very high to the loss of information. A music CD has the advantage that the noise level is very low compared with traditional tape recording.

Compact discs store information as a series of in a spiral around the disk. The string of bits is converted back into sound when a beam of light tracks the CD when it is being played.

Digital signals can be detected easily, since the detector is just looking for a signal of states only, 0 or 1. Even though noise can be present the signal can still be recovered by searching for the sequence of on or off states. Modern communications use digital circuitry to reduce . However, the digital circuits are more than analogue circuits. The required is also greater for digital communications.

Music is normally stored on modern portable devices. The devices are small and compact, and can store of music files.


New music files can be added, and old files can be easily. Care must be taken to make sure that music is not copied .