Code practice oscillator (CB7314E)

Found in a magazine 73 for radio amateurs, this circuit makes use of general purpose transistors and the integrated circuit is still easily found.

| Clique na imagem para ampliar |

Unidirectional motion sensor (CB7281E)
Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The...
Ultrasonic Generator (CB6891E)
Although most common piezoelectric transducers have a reduction in performance at frequencies...
Bicycle Alarm (CB4365E)
This circuit was obtained from a 1986 Spanish magazine Resistor. The magazine no longer exists, but...