This two-transistor circuit is from a December 1964 Radio Electronics. Modern transistors can be tested. The headphone must be high impedance or crystal with a 2k2 resistor in parallel.
Although there is an enormous amount of 12 V voltage regulator integrated circuits, it may be that...
This circuit is from an old Mullard (Philips) manual with applications using the 555. Choosing...
This quick response game was found in a Popular Electronics from the 80s. It uses only discrete analog...