Count to the next top (:00) or bottom (:30) of the minute, or the top of the hour, then add time with the +1, +2 and +5 minute buttons. Reset clears it. With beeps on, you'll hear a beep at 45, 30 and 15 seconds to go, then every second from 10 down to 1. It stays silent at 0, so nothing is heard on air.