Personal television refers to technology that allows the viewer to manipulate live television content sent by the provider (over the air, cable, or satellite). One of the most popular of these technologies is known as the personal video recorder (PVR) or digital video recorder (DVR). The PVR acts much like a video cassette recorder in that it can record live shows to be watched at a later time (time-shifting). The difference lies in the fact that PVRs record the content to a hard disk instead of a cassette. PVRs also constantly record the stream of content the viewer is currently watching, providing the capability to pause, rewind and repeat, and even slow-motion-repeat live television. If viewers intentionally choose to begin viewing a program after the program has begun, they have the capability to rewind and start at the beginning of the show. This also affords the ability to fast forward until the recorded content "catches up" to the live stream. This process allows viewers to skip commercials, a capability that has started a vigorous debate among advertisers worried about the loss of attention to commercials. Most PVRs come assembled as a stand-alone device, or are bundled with devices such as a digital cable or satellite receiver already providing content, commonly referred to as set-top boxes. TiVo, ReplayTV, and Microsoft were among the first companies to introduce PVRs as stand-alone devices. Now many service providers, such as cable and satellite companies, are combining PVR functionality with their digital receivers. For this reason, many scholars believe this technology will spread rapidly.

     One key aspect of the PVR, and central to most new television technologies, is the electronic program guide (EPG). This is a built-in television guide that downloads the television schedule for several days into the future. This allows viewers an easier means of searching for a program and commanding the PVR to record particular programs. The EPG also acts much like a database, able to catalog search terms such as ac­tors, directors, plotlines, and titles, making it easier for viewers to find preferred content.

     Enhanced television allows viewers not only to receive television programming, but also to receive additional information (enhancements) pertinent to the content being viewed. While watching a baseball game, for example, an icon appears on the television screen that can be selected and accessed via the remote control. Doing so may give the viewer individual player statistics, current wind conditions at the ballpark, or other information relevant to the game. Such enhancements could include actor biographies, director's comments, or a full list of program credits. Wink is a current company that provides this type of content and technology to service providers.

     Many of these enhancements work via the Vertical Blanking Interval (VBI) contained in the transmission of data to a viewer's set-top box. The VBI is an extremely brief time interval occurring between different frames being scanned onto the television screen­ comparable to the blank space between frames on film stock. The potential of VBI was understood more fully after engineers realized that closed captioning content could be sent through this VBI. The same concept works for Enhanced Television, but the VBI can carry content, including enhancements, other than video and audio. As an alternative to the VBI, some content providers also use telephone lines, which can be connected to the back of the set-top box, to send the enhancements.

     A truer definition of interactive television takes the concept of enhanced television one step further. In fully interactive television, information between content provider and viewer flows both ways. There are two primary ways this takes place: either through the television setup itself, or through another device such as a computer. The route by which information is sent back to the content provider is called a back channel. The back channel can theoretically operate through the cable or satellite connection originally providing the content or independently through a separate phone line or modem (cable or DSL). This technology is not firmly in place in the United States, but is growing in popularity in Europe. A current concept of interactive television in the United States also allows viewers to use computers simultaneously with television to interact with content. The Game Show Network (GSN), for example, allows users to visit GSN's website on a home computer in order to play along with the contestants in a selected number of shows.

     One element of interactive television developing in the United States is Video on Demand (VOD), an arrangement allowing viewers to order content from their video provider at random times and have it begin playing instantly. The customer searches through a catalogue of shows and chooses content that is then downloaded to their set-top box. Current VOD applications usually sell movies and sporting events but any type of content could theoretically be archived and catalogued. A version of this technology, Near Video On Demand (NVOD), also allows customers to purchase content, although the programming runs in blocks (perhaps beginning every 15 minutes) instead of beginning instantly. This is closer to the concept of the pay-per­-view channels that are currently widely offered.

     More interactive television designs in Europe allow viewers to use television, rather than a second device, as a back channel. Much like enhanced television, viewers can select items on screen with their remote controls and interact with the content. For example, pressing a button during Wimbledon allows the viewer to choose which match he or she wishes to see. Selecting a match other than that on the main video feed gives the viewer the feed and commentary from a different court.

     The ability to send as well as receive information also means that business can be conducted over television, a practice already known as television commerce (t-commerce). In Europe, viewers can order a pizza from Domino's over their television service---during a commercial, the viewer uses the remote control to both order and pay for the pizza to be delivered. This is made possible by accessing what is known as a Walled Garden-viewers are allowed to go online, but only to sites sponsoring the programming or able to make money from the programming. The prospect is that the same t-commerce concept could be successful in the United States, which has much more advertiser­ supported programming than Europe. Product placement in television shows could allow viewers to order that product through their remote controls.

     In some ways, all these versions of interactive television are fundamental alterations of conventionally understood "passive" uses of the medium. It is unlikely, however, that they will completely supplant other practices, such as typical viewing of information and entertainment. They do make clear, however, that the ways in which television has been experienced for more than half a century are not determined by its technological features, which far exceed the uses that have become most familiar to most viewers.