42 kHz oscillator (CB21805E)

This circuit was used as an eraser for old tape recorders. The circuit is from a 1960 Mullard transistor manual.

Timer 4001 2 (CB16316E)
An interesting timer is shown in the figure, using one of the 4 NAND gates of the integrated 4001....
High impedance window comparator (CB6091E)
General Electric suggests this circuit in a 1980s documentation. The operational of the time is...
0 to 9 V x 200 mA power supply (CB18936E)
This simple adjustable source uses a PNP transistor that can be the BD136 for even slightly higher...