Dark activated switch with hysteresis (CB7871E)

Found in a 90s American documentation, this circuit can be used as a shield, just change the coupler for one that uses a phototransistor.

| Clique na imagem para ampliar |

Two-way MW radio (CB18318E)
This old receiver (1967) uses germanium transistors from the time and coupling transformers,...
Pulse stretcher (CB21436E)
This circuit was found in old documentation. D1 can be a diac. | Clique na imagem para ampliar...
Simple oscillator (CB20531E)
This oscillator takes advantage of the 2000 ohms headphone inductance as the oscillator circuit coil....