Electronic circuits use electronic devices to perform functions on signals such as amplification. filtering, rectifying, switching, etc.. Electronics has been a major topic of study in Electrical Engineering for nearly a century. Early electronic circuits used devices such as spark gaps and point-contact crystal diodes to perform signal processing- Later on, vacuum tubes were invented which made electronic communications and control systems widely available, hi the late 1940's, semiconductor devices such as diodes and transistors became available which created an electronics revolution. With these changes in technology, the study of electronics did not change significantly, only the devices changed. The circuits and the methods did not change substantially.