Variable oscillator for code practice (CB7317E)

This circuit is from Popular Electronics from the 90s. The integrated circuit is not very common nowadays.

Temperature sensor TMP390 for -20º C (CB20398E)
This is an application circuit of the Texas Instruments (2019) component datasheet itself. The...
12 V x 2 A power supply (CB17069E)
This conventional 12 V power supply stabilized with 2 A current was found in a 1995 documentation. Its...
100 Hz to 400 kHz oscillator (CB9051E)
This simple oscillator with two general-purpose transistors has its frequency given by capacitor...