In order to measure elapsed time, a standard unit of measure and an instrument to count the units is needed; this is called a clock. An RTC is a clock which is incorporated in an electronic product that keeps track of time, even when the rest of the system is switched off. An RTC is based on a quartz oscillator running at 32.768 kHz, which provides the heartbeat of the clock. It is easy to derive a 1 Hz signal to keep track of seconds, minutes, hours, etc. in dedicated registers in the RTC.