laurance--What time doesd the bus leave for the airport?
soony--I don't know.It used to leave every half hour,but
I think the schedule's been changed.
laurance--Do you know the telephone number to call?
soony--It's Enterprise 7--4700.At least that's what it
used to be.
laurance--Yeah,I'll try it.(PAUSE)They don't seem to
soony--I expect that it's a little too-early.I don't
think they open until nine o'clock.
every half hour:是每隔半小时,类似的短语还有:every other day/
every three weeks/every twenty days