Exactly what it says on the tin. I have a Sound Blaster X-Fi Xtreme Audio Notebook sound card and I was measuring its output frequency using frequency counter connected to the card's output. Frequency was generated using a program called FrequencyGenerator.
This article contains information about Cathodic Protection. Cathodic Protection is an electrochemical means of corrosion control in which the oxidation reaction in a galvanic cell is concentrated at the anode and suppresses corrosion of the cathode in the same cell. Figure 1 shows a simple cathodic protection system.
Electrons flow from the cathode to the anode. Not the other way. There are tubes with three, four, and more elements, but they have these two basic elements. Chemistry The cathode is the electrode of a polarized electrical device, such as a galvanic cell, out of which positive electric current flows.