Tape preamplifier (CB20575E)

With NAB equalization we found this circuit in an English documentation from 1967. The transistors used are germanium types of the time.

Sound Triggered LED (CB4719E)
When this circuit picks up a louder sound it produces a pulse that briefly charges the 10 uF...
Triac Three Phase Motor Control (CB4261E)
In the figure we have the way to make the three-phase control of a motor using opto-diacs. The circuit is...
Diode Test with Oscilloscope (CB4160E)
The circuit shown enables dynamic diode testing with an oscilloscope. We found this configuration in a...