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?