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A sign-on (or start-up in Commonwealth countries) is the beginning of operations for a radio or television station, generally at the start of each day. It is the opposite of a sign-off (or closedown in Commonwealth countries), which is the sequence of operations involved when a radio or television station shuts down its transmitters and goes off the air for a predetermined period; generally, this occurs during the overnight hours although a broadcaster's digital specialty or sub-channels may start up and closedown at significantly different times as its main channels.
Like other television programming, sign-on and sign-off sequences can be initiated by a broadcast automation system, and automatic transmission systems can turn the carrier signal and transmitter on/off by remote control.
Sign-on and sign-off sequences have become less common due to the increasing prevalence of twenty-four-hour-a-day, seven-day-a-week broadcasting. However, some national broadcasters continue the practice; particularly those in countries with limited broadcast coverage. Stations may also sometimes close for transmitter maintenance, or to allow another station to broadcast on the same channel space.
Sign-ons, like sign-offs, vary from country to country, from station to station, and from time to time; however, most follow a similar general pattern. It is common for sign-ons to be followed by a network's early morning newscast, or their morning or breakfast show.
Some broadcasters that have ceased signing on and signing off in favour of 24 hour broadcasting may perform a sign-on sequence between at a certain time in the morning (usually between 4 and 7am) as a formality to signify the start of its operating day (in the United States, the broadcast logging day begins at 6am local time).
The sign-on sequence may include some or all of the following stages, but not necessarily in this order:
Sign-offs, like sign-ons, vary from country to country, from station to station, and from time to time; however, most follow a similar general pattern. Many stations follow the reverse process to their sign-on sequence at the start of the day.
Many stations, while no longer conducting a sign-off and being off air for a period of time each day, instead run low–cost programming during those times of low viewer numbers. This may include infomercials, movies, television show reruns, simple weather forecasts, low cost news or infotainment programming from other suppliers, simulcasts of sister services, or feeds of local cable TV companies' programming via a fiber optic line to the cable headend. Other broadcasters that are part of a radio or television network may run an unedited feed of the network's overnight programming from a central location, without local advertising. During what are otherwise closedown hours, some channels may also simulcast their teletext pages or full page headlines with music or feeds from sister radio stations playing in the background. Some stations, after doing a sign-off, nonetheless continue to transmit throughout the off-air period on cable/satellite; this transmission may involve a test pattern, static image, teletext pages or full-page headlines which was accompanied by music or a local weather radio service.
The sign-off sequence may include some or all of the following stages, but not necessarily in this order:
|Bolivia||Christian sermonette or prayer|
|Germany||Bible reading, responsorial psalm or Christian prayer|
|Greece||Christian sermonette, prayer or psalm|
|Israel||Psuko Shel Yom|
|Saudi Arabia||Quran reading|
|Thailand||Buddhist quote, inspirational message|
|Trinidad and Tobago||Christian prayer|
|United Kingdom||Christian sermonette|
|United States||Christian prayer, sermonette or inspirational message|
|Western Sahara||Quran reading|
In a number of countries closedowns formerly took place during the daytime as well as overnight. In the United Kingdom this was initially due to government-imposed restrictions on daytime broadcasting hours, and later, due to budgetary constraints. The eventual relaxation of these rules meant that afternoon closedowns ceased permanently on the ITV network in October 1972, but the BBC maintained the practice until Friday 24 October 1986, before commencing a full daytime service on the following Monday. Afternoon closedowns continued in South Korea until December 2005. Hong Kong's broadcasting networks (particularly the English-speaking channels) also practiced this until mid-2008. In these cases, the station's transmitters later did not actually shut-down for the afternoon break; either a test-card was played or a static schedule was posted telling viewers of the programming line-up once broadcasting resumes.
During religious holidays or occasions, Doordarshan and Akashvani will broadcast a prayer of any religion through the day, a week or a month (e.g. During Ramadan, a reading from the Quran, a Muslim quote, or a call for Azan and Fajr prayer will be broadcast. During Lent, a Christian prayer, a hymn or a psalm will be broadcast).
During Ramadan, Malaysian public broadcaster RTM operated TV1 24 hours a day instead of signing off. In 2012, TV1 broadcast 24 hours a day during the London Olympics in 2012, due to the time difference. This would become permanent in August 2012, to coincide with their sister channel, TV2 by showing reruns from the broadcaster's archive library and movies on early mornings before start-up.
During the Holy Week in the Philippines, terrestrial television and radio stations continue their regular broadcast schedules (including Lenten drama specials from Eat Bulaga! and It's Showtime) from Palm Sunday until Holy Wednesday. From the midnight of Holy Thursday until the early hours of Easter Sunday (before 4 AM PST on most commercial broadcasters), most non-religious television and radio networks either remain off-the-air due to using the timeframe for annual maintenance of their broadcast equipments or truncate their broadcasting hours and feature special programming such as Lenten drama specials, religious-themed programming and news coverage of various services and rites. Catholic Media Network member stations also follow the latter pattern, broadcasting Easter Triduum services and other similar programming.
Campus radio stations' operations during this time are left to the discretion of their respective schools, colleges, or universities by either closing down on the afternoon of Holy Wednesday or remaining off-air for the entire Holy Week.
On cable and satellite, with the exception of specialty channels that broadcast horse racing, cockfighting, and the like that sign-off and remain dormant during this period, most international networks distributed in the Philippines continue to broadcast their 24/7 regular programming service week-long, while other Philippine-exclusive channels continue with specially-arranged schedules from Holy Thursday to Black Saturday or sometimes regular programming.
There have been notable historic exceptions to the abovementioned protocols, such as