This circuit was obtained in a Popular Electronics of the 90s. The circuit uses integrated from the time, uncommon today. Note that the speaker has a higher impedance than ordinary speakers.
This circuit is from a technical documentation from Motorola from the 70s, and for this reason it is...
We found this circuit in a 1976 documentation. The FET can be BF245 or MPF102 and the power supply...
This miniature railway control circuit was found in an English documentation from the 1980s. The...