The radio signals listed in Table 6 include a voice announcement of UTC
and audio ticks that indicate individual seconds. WWV, the most widely used
station, features a voice announcement of UTC occurring about 7.5 s before the
start of each minute. The beginning of the minute is indicated by a 1500 Hz
tone that lasts for 800 ms. Each second is indicated by a 1 kHz tone that lasts
for 5 ms. The best way to use these broadcasts is to start and stop the stopwatch
when the beginning of the minute tone is heard.