Sinusoidal Oscillator 741 (CB8426E)

Found in a 90s Popular Electronics, this circuit uses a 741 to generate frequencies from 0.1 to 30 Hz. Observe the phototransistor feedback.

| Clique na imagem para ampliar |

Fluid Flow Monitor (CB12461E)
This circuit is from a 1995 technical documentation. The transistor can be a BC558 and the sensor...
Telephone line tester (CB8710E)
Found in a Popular Electronics from the 90s, this circuit checks the presence of voltage on a...
Old Phonograph Amplifier (CB1416E)
The critical component of this amplifier is the output transformer. We found the circuit in an old...