Electronic timer with audible warning and manual reset - used to remind patients to take contraceptive pill

摘要

The timer, which is powered by 6 volts d.c. derived from a battery or mains adaptor, has an LED 'power-on' indicator (D1), a reset push-button switch (R) and a mini-loudspeaker (LS). The reset switch is connected to a commercially-available, integrated circuit timer (IC1). - If the reset switch is not pressed within 26 hours of the last time it was pressed, the IC output switches on an astable multivibrator (Q2,Q3) via a switching transistor (Q1). The output load of the multivibrator is a miniature loudspeaker (LS). The power input is via a diode (D2) which protects the circuit against reversal polarities. (7pp Dwg.No.1/3)