555 Timer, Texas Instruments A range of highly stable precision timing circuits for the generation of accurate time delays or timing pulses. These timers can be operated in monostable (one-shot) or astable (oscillator) mode with timing periods ranging from less than a microsecond to several minutes. In addition to the original bipolar version, low-power CMOS and LinCMOS variants are also available. These devices are capable of longer timing periods and offering a significant reduction in power consumption. The range includes both single (551, 555) and dual (552, 556) versions of the timer.