Sign-on and sign-off

A sign-on (or start-up in Commonwealth countries except Canada) 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 except Canada), 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 sign-on and sign-off 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 24/7 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 at a certain time in the morning (usually between 4:00 and 7:00 a.m.) as a formality to signify the start of its operating day (in the United States, the broadcast logging day begins at 6:00 a.m. local time). The sign-on sequence may include some or all of the following stages, but not necessarily in this order: For television or radio stations that cut off their signal during off-broadcast hours, a test pattern or a static image accompanied by a 400 Hz tone, a 1 kHz tone (or other single-sine-wave tones) or music may be broadcast fifteen to twenty minutes before the actual sign-on.