This simple general-purpose transistor mixer was taken from an article in Electronics Now magazine in March 1994. You can choose a low-noise transistor such as the BC549.
This circuit is from a 1969 Electronics World. The transistors may be modern general-purpose...
This circuit was obtained from Radio Electronics from the 90s. The infrared sensor is of an...
This control panel allows the use of NO and NC sensors, turning the alarm on after 30 seconds...