This organ, played by a probe was found in no old documentation, but it can be easily implemented these days. The integrated circuits are 555. The trimpot allows individual tuning of the keys.
This circuit is from a 1975 Motorola manual. The FET can be the BF245 and the output voltage...
We found this circuit in a 1980 documentation. With basic changes, including transistors that were...
This circuit not only indicates when the battery is on but also when it is low. The circuit is...