This filter for the 300 Hz to 3 kHz range was found in an American documentation from the 90's. The operational amplifier is a double 741.
It can be obtained from Mouser Electronics the new MAX14871 Maxim consisting of a full-wave...
This simple medium wave receiver with a transistor can employ any type of general-purpose...
This circuit generates sequence of pulses in order and times determined by the capacitors in pins...