Two-tone solar buzzer (CB20493E)

This circuit was found in a 1991 publication. The transistor can be a general-purpose type.

High Q Filter (CB25362E)
This 1/2 hertz high selectivity filter was found in the December 1990 issue of Radio Electronics...
Saw tooth converter (CB8930E)
Found in a 1969 EEE, this circuit converts input pulses into linear sawtooth signals, as shown in...
Photo controlled triac (CB8312E)
This circuit was found in an Electronics World of 1968. It can be applied to any modern triac and...