Digital Audio Fundamentals 417or closed and so represent a single bit. This switch may control the voltage in a wire
that allows the bit to be transmitted. In an optical system, light may be transmitted or
obstructed. In a mechanical system, the presence or absence of some feature can denote
the state of a bit. The presence or absence of a radio carrier can signal a bit. In a random
access memory (RAM), the state of an electric charge stores a bit.
Figure 14.5 also shows that magnetism is naturally binary as two stable directions
of magnetization are easily arranged and rearranged as required. This is why digital
magnetic recording has been so successful: it is a natural way of storing binary signals.
The robustness of binary signals means that bits can be packed more densely onto storage
media, increasing the performance or reducing the cost. In radio signaling, lower power
can be used.
In decimal systems, the digits in a number (counting from the right, or least signifi cant
end) represent ones, tens, hundreds, thousands, and so on. Figure 14.6 shows that in
binary, the bits represent one, two, four, eight, sixteen, and so on. A multidigit binary
number is commonly called a word, and the number of bits in the word is called the
wordlength. The right-hand bit is called the least signifi cant bit (LSB), whereas the bit on
Figure 14.6 : In a binary number, the digits represent increasing powers of two from the LSB.
Also defi ned here are MSB and wordlength. When the wordlength is eight bits, the word is a
byte. Binary numbers are used as memory addresses, and the range is defi ned by the address
wordlength. Some examples are shown here.