Metronome using operational (CB22060E)

We found this circuit in an English publication. The transistor can be BC549, and the power supply can be between 5 and 9 V.

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...