Digital electronics, or
digital (electronic) circuits, represent signals by discrete bands of analog
levels, rather than by a continuous range. All levels within a band represent
the same signal state. Relatively small changes to the analog signal levels due
to manufacturing tolerance, signal attenuation or parasitic noise do not leave
the discrete envelope, and as a result are ignored by signal state sensing
circuitry. In most cases the number of these states is two, and they are represented
by two voltage bands: one near a reference value (typically termed as
"ground" or zero volts) and a value near the supply voltage,
corresponding to the "false" ("0") and "true"
("1") values of the Boolean domain respectively.
