Know the basics of open- and closed-circuit filtration designs. Factors to consider when specifying a return line filter system. Selecting the appropriate filtration system when designing a ...

Qucs is a GPL circuit simulator. And if you want the GUI option, you might want to try out QucsStudio, which uses Qucs under the hood, and is free to use, but binary-only.

Closed circuit television may well be one answer to these problems. Television as an educational transmission system has many advantages.