In communication s/m when the data is being transmitted in the form of pn/s the o/p produced at the Rx due to the other bits or symbols interferes with the o/p produced by desired bits. This is called as inter symbol interference. It will introduce errors in defected signals. The ISI arises due to imperfection in the overall frequency response of the s/m.
When a short pulse of duration TD seconds is transmitted through a band limited system then the frequency component contained in the i/p pulse are deferentially attenuated and delayed 6y 8/m.
Due to this dispersion the system will be “dispersed” over an interval which is longer than “To” seconds.
The transmitted pulse of duration TD seconds and dispersed pulse of duration more than T0 seconds.