We found this circuit in a 1974 documentation. Upon receiving an audio signal, it activates a relay with a delay that is set in the 100k pot. The transistors can be the BC548 and the relay must be of the sensitive type of 12 V. The audio signal must come from an amplifier or a piezoelectric capsule. Components with non-standard values can be approximated by current values.
| Clique na imagem para ampliar |
