How do U.S. broadcast network affiliates know when to insert local advertisements?

I am familiar with the systems employed by cable companies to allow them to automatically insert local advertisements in cable network programs. There’s a good overview here, for anyone who is interested.

I am finding it difficult, though, to find any information about how local network affiliates do the essentially the same thing with broadcast network programming. I am being led to believe that the networks somehow distribute a schedule to the affiliates well in advance of the programming feed that permits them to manually schedule their spots, but I’m not sure that I trust my source for this information.

I know that we have a few dopers who work in the industry; I’m hoping that they or others will be able to shed some light on this. Is it really as simple as I’m being led to believe? How are the affiliates informed of the available commercial breaks? Do practices vary by network, or are they pretty uniform? How does this work with sports programming and other live events, where breaks cannot be scheduled in advance?

It’s been awhile since I worked at a broadcast affiliate, but basically, we got a list of the programs as well as the commercials scheduled. We were also told how long the affiliate break was.

This information is provided to the master control operator, and when they saw that the Sprint commercial was airing, and the information said after the Sprint commercial you will see 1:00 of black, that was the cue to run the 1:00 of Joe’s Auto Body and Jenny’s Bait Shop commercials. Most local breaks are scheduled at a halfway point in the show, so you might get two or three national breaks before it’s time for a national/local break.

I don’t think a tone was sent down, but that could be because I worked at a UPN affiliate in Charleston, SC, in the late 90s and well, we just didn’t have the technology. :smiley:

You may sometimes see where the local affiliate has missed the break, and you may see a screen shot with, say, the NBC peacock logo.