But they are turned into electric signals that can then be stored in a computer.

First, the electronics system turns the image into an electronic signal.

The sounds are turned into electrical signals by pick ups.

Those are translated into digital signals and transmitted to the store's computer system.

Radio is one good way to squash energy into a signal carried across the cosmos.

Sounds are recorded through a microphone and turned into electrical signals.

At the other end, the translation occurs again from a chemical into an electrical signal.

Synchronization can also be embedded into a signal on a single wire.

Sound waves are converted into an electrical signal inside the recorder.

Converting composite video into separate signals is relatively easy but I'm not sure why you want to do it.