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.
In a galvanic (voltaic) cell, the anode is considered negative and the cathode is considered positive. This seems reasonable as the anode is the source of electrons and cathode is where the electrons flow. However, in an electrolytic cell, the anode is taken to be positive while the cathode is now negative. However, the reaction is still similar, whereby electrons from the anode flow to the positive terminal of the battery, and electrons from the battery flow to the cathode.