This 1 kHz TTL oscillator uses 3 inverters of a 7404 integrated circuit. The circuit is from a Popular Electronics from the 90s.
The transistors of this amplifier for 8-200 headphones may be the BC548 or equivalent to replace...
The purpose of this simple stabilized source, obtained in a documentation from the 70s, is to...
The circuit shown in the figure is from a 1976 publication. Equivalent tunnel diodes can be used....