Leeuwrik was requested to build a speaking clock for the municipal telephone service of The Hague
His experience with sound film made him decide to use optically recorded speech, looping on a large drum
There were loops for the hours and for the minutes, each one read with a photodetector
Every minute the clock gave an electric pulse, causing the mechanism to shift to the next minute
Every hour, the minute mechanism was reset (and every day the hour mechanism), the clock was accurate within one minute only
The female voice was provided by the then 24-year-old school teacher Cor Hoogendam, hence the machine was nick-named Tante Cor (Aunt Cor)
The speaking clock came into service at November 9, 1934 and could be reached by dialing 393131
The service became so popular, that in 1935 a second machine was ordered and built
Even during the Nazi occupation in World War II, the speaking clock was called over two million times a year.
In 1969 this system was decommissioned and replaced by a machine that looked like a record player with three pick-up arms
The speaking clock was now nation-wide available through the number 002 and was much more accurate, telling the time in 10 second intervals followed by a beep, indicating the precise moment
The text was spoken by actress Willie Brill and had the following format: "Bij de volgende toon is het .
seconden" (at the following tone, it is .
The service was now called over 130 million times a year.
Finally, in April 1992, the whole machinery has been replaced by a digital machine with no moving parts
The (digitized) voice has been provided by actress Joke Driessen and the clock is being kept accurate by German longwave transmitter DCF77
In accordance with international guidelines (the double-zero should be used as an international prefix), the number 002 has been replaced with 0900-8002
Though nowadays many people have digital wrist watches, mobile phones or computers telling the time accurately, the service is still being called approximately four million times a year, especially around New Year's Eve and when the daylight saving time changes.
The speaking clock (Norwegian: Frøken Ur, meaning Miss Clock) in Norway was in service between 1932 and 15 January 2007 14h00 local time
The service could be reached by dialling 09170 (1999–2007), and 170 (until 1999)