This circuit uses a parallel resonant crystal to control the frequency. The circuit is from Radio Electronics magazine, February 1993. Equivalent transistors can be used.
This circuit was obtained from ancient documentation using transistors of the time. The circuit...
I found this circuit in an old Argentine publication from 1973. The components are no longer...
This ammeter measures currents in 5 ranges from 50 uA to 0.5 A using a 40 uA instrument, which can be...