Doorbell Circuit

This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit includes a CMOS 4026 counter display driver IC to count your visitors. The count may be expanded for up to 99 visits by cascading two CMOS 4026 IC`s and using an additional 7 segment display. This is achieved by wiring pin 5 ( the 10`s output ) of the first CMOS4026 to pin 1 (the clock input) of the second IC...

This is a circuit that could be used as a doorbell system like those that most homes have. From what I can tell, pressing the switch triggers the IC to oscillate and send electricity through the transistors to power the speaker. The IC type is not listed, but I am guessing that it is a 555 Timer...

This simple and cost-effective door bell circuit is based on IC 8021-2 from Formox Semiconductors (Website address: fortech@mantramail. com). It is an 8-pin DIP IC whose only four pins, as shown in the circuit, have been used...