In this method, the carrier
wave is switched from one level to another by the binary
signal. During the '1' State, the 'mark' signal increases
the carrier level, while during the '0' state or 'space'
signal, the carrier level is reduced.
Modulation with
OOK
This method is also termed
as 'On'-'OFF' keying when the carrier is made OFF during
space periods and was originally used in wireless telegraphic
circuit. The wave transmitted is termed as ICW transmission.
If the carrier is represented by
then the modulated signal
using OOK may be written
as:
= 0 for space
signal
Carrier transform yields the following
results.
Thus, the effect of ON-Off keying is
to produce a pair of upper and lower side bands, the
bord-width at such a system is, therefore, twice the
highest frequency present in the pulse signal.
then the modulated signal 
