Also known as ISI. In digital audio or video a clock serves as a timing reference for a system. Everything in digital audio and video is related to a clock. There are specified numbers of operations per period of time and they all must be carried out at a consistent speed in order for the device to work properly. The ‘mechanism’ of a digital clock is a pulse. Intersymbol interference (ISI) is reduction or smearing in the distinction of a pulse caused by overlapping energy from neighboring pulses. ISI may result in data dependent deterministic jitter.