This crystal oscillator is indicated for the calibration of IF steps of common radio receivers. The transistor admits equivalent as 2N2222 or BF494. The circuit is from an old American publication.
This circuit is from the time when cars used contact breakers. This 80's version measures the dwell...
This circuit is for traditional old-style telephone lines found in an American 1980s...
This circuit with RIAA equalization is from 1985 US documentation. The circuit has a flat response...