Preamplifier stage (CB8934E)

This circuit is from a 90s Popular Electronics. It appears elsewhere on this site. Q1 can be any general purpose transistor.

Electronic Switch (CB16908E)
This circuit controls a relay in a bistable way by touching the sensors type NF (CH3) and NO...
Multi Tone Siren (CB436)
This circuit produces modulated tones in a loudspeaker. The effects can be adjusted by the...
Relaxation Oscillator Using PUT (MSB075E)
This is a simulation of a Relaxation Oscillator using a programmable unijunction transistor (PUT). The...