Timers are based on the quartz clock of the ClassPad and allow to realize actions with regular intervals. Some timers are existing. The one which is accessible directly by ClassPad SDK (PegTimer) is limited : his minimal period is one half-second. Other timers have been discovered, as the TME (Timer Units) called "SH3Timers" with a 3Mhz frequency and which allow interruptions, or as the RTC (Real Time Clock) which allow to obtain the time.