Optical potentiometer (CB22159E)

This voltage-controlled potentiometer using an LDR was found in an English documentation. LDR is common and LED of any type.

Low Pass Second Order Filter 741 (CB25818E)
This unity gain circuit was found in the February 1995 Electronics Now magazine. The frequency is 10 kHz,...
Pulse Compressor and Expander (CB6658E)
Found in a 1967 Electronic Design, this transistorized circuit compresses and then expands a pulse....
Simple pulse extender (CB8921E)
This TTL pulse stretcher or stretcher was found in a 90's EDN. The time constant R x C1 determines...