This circuit is used in a LASER detection system to avoid echoes from short distances in systems up to 1 mile. The circuit is from a 1967 documentation.
Using a voltage comparator, we find this AND gate on a Popular Electronics from the 90s. The...
This crystal oscillator circuit is indicated for use as a frequency reference in the calibration...
Any operational amplifier can be used in this circuit. The 741 is the most common. Power supply must...