Buffer 4049 (CB26316E)

The purpose of this circuit found in a 1990s Popular Electronics is to increase the current capability of CMOS stages.

LM3914 with Overscale Alarm (CB25112E)
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
TTL Siren (CB18966E)
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
Crystal Controlled Signal Source (CB6147E)
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...