Local insertion
From Wikipedia, the free encyclopedia
In broadcasting, local insertion is the act or capability of a broadcast station or cable TV system to insert or replace part of a broadcast network feed with content unique to the local station or system. Most often this is a station identification (required by the broadcasting authority), but is also commonly a television commercial or sometimes a radio ad, or a traffic or weather report. A digital on-screen graphic ("dog" or "bug"), commonly a semi-transparent watermark, may also be keyed (superimposed) with a TV station's logo over the network video using a character generator and genlock.
Automated local insertion used to be triggered with in-band signaling, such as DTMF tones or sub-audible sounds (such as 25Hz), but is now done with out-of-band signaling, such as analog signal subcarriers via communications satellite, or now more commonly via digital signals. Broadcast automation equipment can then handle these automatically. In an emergency, such as severe weather, local insertion may also occur instantly through command from another network or other source, such as the Emergency Alert System. In this case, the most urgent warnings messages may interrupt without delay, while others may be worked into a normal break in programming within 15 minutes of their initial issuance.
In the United States, insertion can easily be heard every evening on Delilah, a nationally-syndicated radio show, where the host does a pre-recorded station-specific voiceover played over a music bed from the network. When she says "this is Delilah", her voice (often in a slightly different tone or mood than what she has just been speaking) then says "on B98.5 FM" when heard on WSB-FM in metro Atlanta, for example. Listeners to other stations hear their own station's moniker or ID instead.
Various TV morning shows, such as Good Morning America and The Today Show, also have a local news break for five minutes prior to each "bottom" half-hour (:25 to :30), though the national feed continues for stations that do not wish to "break away". This also occurs with news on National Public Radio's Morning Edition and All Things Considered, which are on during the morning and evening rush hours, respectively.
Broadcast translators may also have local insertion, though this is very limited to identifying the repeating station's callsign and community of license separate from its parent station. In the U.S., the FCC also allows up to 30 seconds per hour for fundraising to keep the translator service on the air.
