There might be long 'intervals' during/in which nothing happens.
There are signs 'at' regular 'intervals' along the outside wall.
There will be a 20-minute 'interval' between acts one and two.
(..) - She got us up to check it out. - A transmission? Out here? - Yeah. - What kind of a transmission? Acoustical beacon. It repeats at intervals of seconds. - S.O.S? - I don't know. Human? - Unknown. - Well, so what? (..)1979 Alien