View r3111xxx1a-c-series datasheet:

’98.Dec.05 LOW VOLTAGE DETECTOR R3111xxx1A/C Series OUTLINE The R3111 Series are voltage detector ICs with high detector threshold accuracy and ultra-low supply current by CMOS process, which can be operated at an extremely low voltage and is used for system reset as an example. Each of these ICs consists of a voltage reference unit, a comparator, resistors for detector threshold setting, an output driver and a hysteresis circuit. The detector threshold is fixed with high accuracy internally and does not require any adjustment. Two output types, Nch open drain type and CMOS type are available. The R3111 Series are operable at a lower voltage than that for the RX5VL Series, and can be driven by a single battery. Four types of packages, TO-92, SOT-89, SOT-23-5 and SC-82AB are