A scrambler is an electronic device that alters or mixes broadcast sound and telephony information so that people can only receive and understand it through a specific device (such as a decoder, etc.). Its function is equivalent to an encryption device. It is an important means to ensure that the content of radio waves and TV will not leak privacy and prevent eavesdropping.

When I was working as a microcontroller a long time ago, I knew that inductive coils such as motors and relays needed a reverse freewheeling diode in parallel to prevent the reverse electromotive force generated by the inductance from damaging the coil. Recently, I suddenly thought about how to thoroughly understand the generation and direction of this back electromotive force. During the period, I consulted relevant materials, and I also gained some new understandings, which corrected the previous misunderstandings.