Signals & telecom · the six-pip time signal
The Pips Time Signal
The BBC-style time signal: five 1000 Hz pips one second apart and a longer sixth pip on the hour. Play it on demand, watch the countdown to the next hour, or leave it armed to sound automatically. The tones are scheduled against the audio clock, not a timer loop, so they stay even.
This is a demonstration, not an official time source. Accuracy is limited by your device clock, and the automatic pips only fire while this browser tab stays open.
1000 Hz is the BBC standard. Some other broadcasters use 800 Hz or 1500 Hz.
Off by default. When on, the tab must stay open and the machine awake - the browser suspends timers and audio in a backgrounded or sleeping tab, and the pips will be missed. The pattern is armed a few seconds before the hour and aligned to the audio clock.
Ready. Press play to hear the six pips.
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To next hour
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Next hour at
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Short pip
0.1 s
Long pip
0.5 s
Spacing
1.0 s
Pips
6
The six-pip pattern
Five short pips are emitted at one-second intervals, then a sixth pip that starts exactly on the hour and lasts five times as long. The start of the final pip is the reference instant: it coincides with the top of the hour. The frequency is nominally 1000 Hz - a clean, easy-to-hear tone that cuts through programme audio without being shrill.
Why the last pip is longer
The lengthened sixth pip disambiguates the end of the sequence. With six identical pips there would be no way to tell, by ear alone, which pip marked the hour. The long pip gives a single, unmistakable instant to set a clock against.
The leap-second case
UTC is adjusted to follow the Earth's rotation. When a positive leap second is inserted the BBC adds a seventh pip after a one-second pause; a negative leap second, never yet required, would remove one.
Accuracy
Broadcast pips are generated from an atomic-clock reference, so their spacing and the hour mark are accurate to well under a millisecond at the transmitter. What you hear, and what this page can recreate, is limited by the network path and your own device clock.
What are the pips, exactly?
The pips are the BBC's time signal: six short tones, the last one longer. Five pips are 0.1 s long and are spaced one second apart; the sixth, on the hour, is 0.5 s long. The rising long pip marks the exact top of the hour. They have been broadcast since 1924 and are generated from an atomic-clock reference, so within their one-second grid they are a genuine time signal rather than a decoration.
Why is the last pip longer?
Because one pip is reserved to mark the boundary. If all six were the same length and the same pitch, listeners could not tell which pip was the hour and whether the sequence had finished. The longer sixth pip makes the hour unambiguous and gives a clear instant to set your watch to - the start of that pip is the top of the hour. It also lets broadcasters identify the tone within the sequence.
What about leap seconds?
UTC is occasionally adjusted by one second so it tracks the Earth's rotation (the last was added in 2016). The BBC inserts a seventh pip for a positive leap second, after a one-second pause, so the sequence becomes six pips, a gap, then an extra pip. Removing a second (a negative leap second, which has never yet occurred) would drop a pip. For most of the year the six-pip pattern is unchanged.
Is this an accurate clock?
No. The tone frequencies are exact, but the timing depends entirely on your device clock and the AudioContext clock, which are synchronised to your operating system, not to an atomic reference. Use this page to hear and understand the signal, not to set a precision clock. On the hour it plays the pattern you asked for; the truth of the time is your computer's business, not this page's.
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