Television networks are handled and broadcast differently in the US. One major company 'The Network' (There are 8 main commercial networks, the biggest four being ABC, CBS, NBC, and Fox. The smaller 5 are WB, UPN, PAX and PBS) is responsible for buying and in some cases producing programming, but does not broadcast it directly. Instead, the network relies on local stations in all the different regions (or 'markets') to distribute the programming to the population. These are called 'affiliates' Affiliate stations hand over control to the networks at certain times, notably mornings and peak time (called primetime in the US), as well as afternoon lineups of soap operas. The networks handle scheduling during these time periods; if a show gets pulled, it is across all stations of the network. During these periods, programming is branded under the network name only, although in most cases the local stations do put their own logos on the screen coming back from break or during network promotions. When the affiliates are not broadcasting network programming, their own lineups consist of home-grown output, mostly local news, of which there is a LOT more of than in the UK, or syndicated programming. Syndicated programming is similar to networked programming, although the distribution is not handled by the network and the local station has control of where to put it. Affiliates in the major cities/markets are owned by the networks and are called 'Owned and Operated' stations - or O&Os. But for the most part, this is the exception to the rule - most stations are owned by independent companies. Generally, branding of affiliate stations nowadays is network/channel number. You see a lot of ABC 7s, NBC 4s, and CBS 2s, among the O&O station groups, but there are still a lot of affiliates that go with just the call letter identifications "WUSA 9", "KARE 11", even a "catchy" name! (WXIA in Atlanta is "11 Alive"), some even just use a channel number. We believe Fox that all affiliates have to use Fox-approved names and channel logos, which is why all the Fox affiliates look exactly the same. Pax is different, identification on Pax's affiliates is usually just "PAX" with an ID at the top of the hour. Some Pax affiliates, however, have tried local news and do have different, separate identifications. Scheduling is controlled by Pax themselves; this is more like ITV now. PBS, even though it gets government funding like the BBC, is more like how ITV used to be. Less a network than a collection of separate affiliates who produce the programming that is shipped to PBS and then "networked" to the local stations. They even used to have frontcaps until recently. Some PBS affiliates embrace the national PBS brand and graphical look. Some, however, go their own way, such as WHYY in Philadelphia, which emphasises their own look over PBS'.
Call Signs or Call 'letters' have been assigned since 1927 by the FCC (Federal Communications Commission) initially to radio stations to identify them from all the different kinds of radio services over land, sea, air and space. They serve three purposes, (1) identify the nationality of the station (2) the type of station (3) the individual station. Call signs, in effect, are like license plates of broadcasting. Broadcast stations in the US are assigned call signs by the FCC beginning with K or W. Generally speaking, those beginning with K are assigned to stations West of the Mississippi River and in U.S. territories and possessions, while those beginning with W are assigned to broadcast stations East of the Mississippi River. Since the beginning of radio broadcasting, stations have had the privilege of requesting specific call signs. In requesting their preferences for certain letters of the alphabet, broadcasters have presented combinations of names, places or slogans. For example, the letters NBC are used for stations owned by the National Broadcasting Company, CBS for those of the Columbia Broadcasting System, and ABC for the American Broadcasting Companies. Examples of individual station call letters are: WGN, Chicago ("World's Greatest Newspaper"), WNYC, New York (New York City municipal station); KAGH, Crossett, AK, ("Keep Arkansas Green Home"); WIOD, Miami ("Wonderful Isle of Dreams"); WLS, Chicago ("Worlds Largest Store"); WACO, (Waco Texas); WTOP, Washington, D.C. ("Top of the Dial"); KFDR, Grand Coulee, Washington, (Franklin D. Roosevelt); WCFL, Chicago ("Chicago Federation of Labor"); WMTC Vancleve, KY, ("Win Men to Christ"); WGCD, Chester, S.C. ("Wonderful Guernsey Center of Dixie"); Educational TV station WXXW, Chicago, uses the Roman numerals for its channel 20; and KABL, Oakland, CA, selected its letters to represent San Francisco's famous cable cars. If a new broadcast station makes no specific request, it is assigned a call sign by the FCC. Since 1946 the FCC has not guaranteed specific call signs to be granted prior to the grant of a construction permit or special temporary authority. As broadcast stations began to increase in the early 1920's, the three letter call sign could no longer accommodate the growing number of stations, making it necessary to add a fourth letter. With the advent of TV in 1941, new call signs for all such stations were not assigned. Rather, since many TV stations were operated by the same AM licensee at the same license area, the general practice was for the associated TV station to simply add "-TV", to the call sign of the co-owned AM station. (Information from the FCC website - www.fcc.gov)
In 1996 The United States Congress and the tv industry designed a voluntary rating system, known as The Parental Guidelines. Similar to cinema ratings, they are designed to provide parents with more information about the content and age appropriateness of programmes. Displayed in the top left corner of the screen, at the beginning of a programme, these are the symbols and what they mean.. TVY - ALL CHILDREN This would mean the programme is produced specifically for children ages 2-6 TVG - GENERAL AUDIENCE Suitable for all ages. Programme would contain little or no violence, no strong language, no sex. TV14 - PARENTS STRONGLY CAUTIONED This programme would contain material unsuitable for children under 14 years. Such as intense violence, sex, strong coarse language. TVY7 - DIRECTED TO OLDER CHILDREN Viewers aged 7 and above. Themes may include fantasy violence or comedic violence. TVPG - PARENTAL GUIDEANCE SUGGESTED. This programme may contain moderate violence, sexual situations, coarse language. TVMA - MATURE AUDIENCES ONLY This programme designed specifically for adults. May contain explicit sex, crude or indecent language.