Often we only recognize important moments in retrospect -- but we already know that this Friday will be a watershed day in media. When analog TV signals are erased from the U.S. airwaves and replaced by digital, a small percentage of households will lose TV access, despite the availability of converter boxes and government coupon programs; but many others have been or will be introduced to new programming, ads and technologies as a result of the transition -- changes that could shift their viewing behavior forever. The newest media technology Ownership and Trend study by Knowledge Networks shows that 27% of TV homes have at least one set that uses through-the-air signals only. Of these homes, 19% say they are simply abandoning these "rabbit ears" sets altogether, while 81% are replacing them with digital sets or upgrading them for digital reception. We found that 26% of all TV households have made some sort of a purchase -- a converter box (18%), an HD or digital TV set (8%), or a new cable or satellite TV subscription (5%) -- to prepare for the digital transition. These "transition upgrades" in some cases were more common among groups at risk of losing their TV access because of the switchover. So, apart from the relatively few who may end up being disconnected, we also find that some in these high-risk groups are gaining access to new channels and technologies. For example, African-American (20%) and Hispanic (22%) TV households were more likely than white (15%) ones to have bought a digital converter for a broadcast-only set. And while one in four (26%) homes earning less than $30,000 a year bought a converter box, the proportion drops to almost one in seven (15%) when income rises to $50,000 or more. Clearly, buying a converter box is the least costly way to make the digital upgrade; but even this approach is likely to give people - in a market like the New York/tristate area - access to two dozen or more "side channels" they have never seen before. (We are not asserting that these are the only groups at risk in the transition; but, contrary to some published reports, we did not find that older people are at high risk of losing their TV access in the transition.) In addition, 8% of all TV households bought an HDTV or digital set just for the digital changeover - a proportion that rises to 11% for each of our three at-risk groups (low-income, African American, Hispanic). In a report to be released next month, we will show that access to HD programming changes how people approach television; they are more likely to check high-definition channels first when looking for something to watch, and more likely to say commercials in HD programs are relevant to them. These behaviors are essentially the same regardless of HD tenure; in other words, they do not appear to be short term. And the digital transition is bringing them to homes that might otherwise not have experienced HD until prices came further down, or maybe never. Among those who have adopted a new TV service for the transition, we found that 63% chose cable, while virtually all others got satellite. These new subscriptions were not statistically higher among the at-risk groups. Thanks to the transition to digital TV, new technologies and channels are coming into a variety of homes -- including lower-income and ethnic ones. Something tells me we will be tracking the effects of this new TV world for many years to come.