Wizard API updated!
Tim Boudreau has released a new version of the Swing Wizard library (version 0.997) that fixes the WizardException bug reported in JavaWorld's recent Open Source Java Project profile. The article's examples have been reworked to test out the new, improved WizardException. Thanks, Tim, for this helpful fix!
Open Source Java Projects: The Wizard API

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The evolution of cable television to interactive communications service provider

By Jim Connors, JavaWorld.com, 10/01/96

The first foray into cable television appears to have taken place simultaneously in both Pennsylvania and Oregon in the late 1940s and early 1950s. At the time, the fledgling television industry provided broadcast signals only to the most populous (that is, economically advantageous) areas. For those regions that had poor TV reception either because of obstructions or long distances from signal transmitters, cable television provided a workable solution. Essentially, the early cable providers constructed large antennas on hilltops or buildings for improved TV reception, and then strung coaxial cable from the antenna to the local community. Out of this environment the acronym CATV, representing Community Antenna Television was born.

With the advent of satellite broadcasts to cable systems in the 1970s, cable operators were able to provide more channels than were available over the traditional airwaves. Because of these value added capabilities, cable television made significant inroads into markets where TV reception was already reasonably acceptable. Additional services such as specialty channels and pay-per-view have brought the cable industry to where it is today: approximately 63% of American households have cable TV, and cable service passes by about 95% of all U.S. residences.

The cable industry is less than 50 years old, and yet with such a large market penetration, is already reasonably mature. In searching for growth opportunities, the much ballyhooed National Information Infrastructure (NII) or "Information Superhighway" provides an opening for cable television to build upon its extensive architecture and experience to deliver the necessary features for the upcoming information age.

System architecture

Traditional cable television systems can be divided into five major sections. Figure 1.1 depicts graphically the "tree and branch" architecture.

The headend is the center of CATV activity. It is here where external signals such as satellite, microwave, and local TV station broadcasts are received from the various types of deployed antennas. Additionally, locally produced and pre-recorded programs can be introduced into the mix. Ultimately it is the headend's responsibility to process, combine, and assign a channel frequency to all signals destined for cable distribution.

A number of trunks, originally constructed out of large diameter coaxial cable, carry the signals from the headend to a series of distribution points. Trunk cables share the same properties as do generic transmission lines with regard to attenuation; in order to maintain adequate signal strength over long distances, amplifiers are required at regular intervals. Much experience has shown that on average, amplifiers need to be spaced approximately 2,000 feet apart. Only a finite number may be cascaded (approximately 30-40), as each amplifier introduces additional noise and distortion to the signal. There are well known thresholds of signal distortion, above which, TV picture quality will be affected.

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