Dynamic compressor (CB21762E)

This circuit was found in a 1977 publication for radio amateurs. Transistors are common general-purpose types of the time.

Analog Tachometer (CB1366E )
This circuit converts pulse frequency to current, which is indicated on an analog instrument. The...
Active cycle meter (CB7072E)
Based on an LM317T, this circuit found in Popular Electronics works with signals of frequencies up to...
LM5176 Buck Boost Synchronous Controller - Texas Instruments
The Texas Instruments LM5178 Buck-boost controller is capable of operating in the 4.2 to 55 V (60...