This variable filter that lets frequencies from 500 Hz to 1500 Hz pass through was found in a Popular Electronics from the 90's. The operational amplifiers are the 741.
This circuit was found in Philips documentation from 1965. No information was given about the...
This control allows to start or stop a motor up to 3 or 4 A with a low intensity signal. The...
We found the circuit of this Japanese transistorized commercial receiver in a documentation from...