每隔（一定时间或距离）
repeated after a particular period of time or a particular distance
In the event of fire, the alarm will sound at 15-second intervals/at intervals of 15 seconds. 发生火灾时，警报每隔15秒就会响一次。
Old family photos are featured at intervals throughout the book.
The lights flash at intervals of exactly 5.3 seconds.
Markers were placed at intervals along the route.
Gas firms have produced plans to drill at intervals of 10 acres.
See also: interval (TIME/DISTANCE)