“Prior to the 1990s, cable
television
systems were not intended to be general-purpose communications
mechanisms.
Their primary and often sole purpose was the transportation of a
variety
of entertainment television signals tosubscribers. Thus, they needed to
be one-way transmission paths from a central location, called a
headend,
to each subscriber’s home, delivering essentially the same signals to
each
subscriber. The signals are intended for use with the
consumer-electronics
equipment that subscribers already own.  This equipment is built
to
operate
on the current U.S. television technical standard called NTSC after the
organization that created it in 1941, the National Television Systems
Committee.
This black-and-white television standard was modified in 1953 to
provide
compatible color information to color television receivers, and again
in
1984 to add compatible stereo sound.

“The original purpose for cable
television
was to deliver broadcast signals in areas where they were not received
in an acceptable manner with an antenna. These systems were called
community
antenna television, or CATV. In 1948, Ed Parson of Astoria, Oregon,
built
the first CATV system consisting of twin-lead transmission wire strung
from housetop to housetop.  In 1950, Bob Tarlton built a system in
Lansford,
Pennsylvania, using coaxial cable on utility poles under a franchise
from
the city.”

“In most CATV systems, off-air signals
were
not available or were very weak because of the terrain or the distance
of the receiver from television transmitters.  In some areas, such
as
New
York City, multiple signal reflections and shadows cast by buildings
made
recept