A clock is not a playlist
A playlist is a list of specific songs. A clock template is more abstract: position 1 is an uptempo track from category A, position 2 a jingle, position 3 a medium track from category B, minute 15 the weather. The clock names no titles. Only when the hour is prepared does the planner pick a real track for each slot that satisfies the rules: right category, right tempo, not played too recently, not the same artist as three tracks ago.
That distinction is the heart of radio automation. One clock produces 24 different hours a day that all sound the same, because the shape is fixed and only the content changes.
What a slot can hold
A slot has a type. In NexRadio that includes music (with category and tempo), jingle (from a rotation group, so the same sweeper does not play every hour), AI presentation (a template that says what the voice will do: introduce a track, lead into the news, read a listener request), weather, news, and external content such as a bulletin from outside. A slot can carry a minute anchor: this element must fall at :30. The slots between shift according to their real durations.
Every hour ends with a fixed anchor we call Break:59. It is not audio but a marker: the hour ends here, and slot 0 of the next hour starts after it. Everything in the clock is planned against that anchor.
How the clock gets filled
Well before the hour starts, the planner compiles the next hour: it walks the slots, picks a track per slot and computes start times from the cue points of the chosen tracks. The result is a concrete list with times that appears in the playlist and that the playout engine plays one by one. If something changes in between, say a listener request or a presenter skipping a track, the times are realigned to what is actually playing.
Key principle: the clock is the source. The playout layer adds nothing and removes nothing. If a gap appears, it is a fault in the clock or the library, and that is where you fix it, not with an emergency patch during the broadcast.
What goes wrong with a thin clock
A classic mistake: a clock with eleven music slots and a library full of three-and-a-half-minute radio edits. Eleven times three and a half is forty minutes. The hour is twenty minutes short. What happens next depends on the hour-boundary mode, but no mode can invent music. The fix is always: more slots, longer tracks, or both.
The opposite, an overfull clock, is less serious. In strict mode the last song is faded at the top of the hour; in the loose mode the last music slot is skipped if it no longer fits. That is intended behaviour, not a fault.
Clocks per daypart and per show
A station rarely has one clock. Mornings want more presentation and news, nights want long tracks and little talk. So you assign clocks to hours in a weekly schedule: clock Morning on weekdays 06–10, clock Night 00–06, and so on. A three-hour show with its own presenter can have its own clock, with templates that carry that presenter's name.
In NexRadio you build clocks in a visual clock builder, save them with a revision and assign them in the schedule. A running hour that is already prepared keeps its old clock; the change applies from the next hour still to be compiled.
Frequently asked questions
How many slots should a clock have?
Enough to fill the hour with the shortest tracks in the category. Calculate with the shortest, not the average duration. An hour with fourteen music slots, two jingles, weather and two talk breaks is a normal fill for a pop format.
Can I change a clock while the station is on air?
Yes. The change applies to the next hour that has not yet been prepared. The current hour and an hour already prepared keep their existing plan.
What is Break:59?
The anchor at the end of every hour. It is not a sound; it marks where the hour stops and the next begins. All elements in the clock are planned against it.