Tom Donaly wrote:
"DC stands for Direct Current,. What is a static direct current, charged
particle?"

My dictionary says d-c: An essentially constant-value current that flows
in only one direction." Another definition says: "It may be continuous
or discontinuous. It may be constant or varying."

Static means stationary or fixed. A static charge is the accumulated
electrical charge on an object.

Terman writes on page 288 of his 1955 edition:
"An amplifier having a frequency range extending from a low value up to
the order of a megacycle or higher is termed a video amplifier."

Black level is that level of the picture signal corresponding to the
maximum limit of black peaks. White level is the carrier-signal level
which corresponds to maximum TV picture brightness.

Alternating current cycles, regularly, increasing and decreasing
periodically.

An alternating current is assumed to be sinusoidal unless otherwise
specified, but it could, for example, be triangular, square, or it could
have some other form. If the wave is symmetrical about the zero axis,
any number of complete cycles will have zero as their average value.
Most amplifiers and transmission systems are not directly coupled. They
use capacitors or transformers between stages. These can`t pass direct
current, so this reference is lost in transmission unless other steps
are taken for its replacement.

The effective value of a sine wave thet does the same work as direct
current does is 0.707 x the peak value of the sine wave. Average of the
sine wave is different. It is the average of many equally spaced values
taken along the course, from awro to zero through one complete HALF
cycle of the wave. This works out to 0.636 x the peak value of the sine
wave (0.9 x 0.707).

Best regards, Richard Harrison, KB5WZI