Old superheterodyne (T1611E)

Found in a 1949 Radio Electronics, this commercial circuit was found in many countries, including Brazil.

Three Hours and Half Timer (CB4310E)
This circuit was found in a 1989 documentation. The circuit directly controls a power load by the use...
FM transmitter (CB15079E)
This small telephone transmitter uses a telephone capsule as a microphone. The L1 coil has 4 to 5...
Fluorescent Emergency Light (CB17420E)
This emergency light circuit does not include a battery charger or an intelligent system to...