Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This 1/2 hertz high selectivity filter was found in the December 1990 issue of Radio Electronics...
Found in a 1969 EEE, this circuit converts input pulses into linear sawtooth signals, as shown in...
This circuit was found in an Electronics World of 1968. It can be applied to any modern triac and...