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.
This circuit was found in the September 1996 issue of Electronics Now magazine. The sound provided has...
We found this circuit in a March 1961 Radio Electronics magazine. This circuit reaches 100 MHz...
Using the M1575 this switching converter was found in National Semiconductor documentation from...