Found elsewhere in this section, but from other sources, this circuit is from a 1964 Electronic Design. The transistor is from the era and the power voltage depends on this component.
From an audio signal, this circuit gets two signals of the same amplitude and opposite phases....
This conventional relay light detector circuit uses a 741 as a voltage comparator. The sensitivity...
In this circuit the photo-transistor signal is amplified by a Darlington step and then applied to a...