Very loud pulse buzzer

Many battery-powered alarms consume excessive current during operation. Some of the most notable noise generators, such as the unit shown below, use piezoelectric sound generators with swept tones. When operating with a 9-volt battery, these units typically consume 100 mA or more. In many applications, a continuous alarm sound is not required. Locating balloons or rockets are examples where a loud sound is needed but with low average power consumption. To reduce the average current, the device can operate with pulses of short, 0.05-second chimes, occurring every two to three seconds. This reduces the average current by a factor of 60. Therefore, by making the alarm chirp, the current consumption drops from 100 mA to just 2 mA. The circuit below generates the pulse sequence required to produce these short but very loud chimes.