This astable for the audio band can be used as a signal injector or alarm. The circuit is from a publication from the 1970s, using germanium transistors from that time. The circuit will work with current PNP transistors, such as the BC558 and power supply from 6 to 9 V. The capacitors determine the frequency of operation and can be changed. For sound reproduction, a piezoelectric capsule can be used.
| Clique na imagem para ampliar |
