The RE46C120 is a low power CMOS ionization type smoke detector IC. With a few external components this circuit will provide all the required features for an ionization type smoke detector.An internal oscillator strobes power to the smoke detection circuitry for 10.5mS every 1.66 seconds to keep standby current to a minimum. A check for a low battery condition is performed every 40 seconds when in standby. The TONE input allows for selection of a temporal pattern or continuous tone. The temporal horn patter