A simple transistor based electronic siren

For some time, hobbyists have relied on dedicated sound generator ICs, such as the UM3561 , UM3562 to build compact alarm and siren circuits. Unfortunately, this device is becoming increasingly difficult to find in the market. The manufacturer of the chip, United Microelectronics Corporation (UMC), is still around. However, they are no longer producing the UM3561 or UM3562. As part of a fun…