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| | Electronic clocks are based on counting the oscillation periods from
stable quartz generator with the help of divisor meters and displaying
the readings on electronic display: Electro-luminescent vacuum
display, light emitting diode or LCD through decoders. First
electronic clocks were made on separate lamps and then transistors and
integrated circuits. Then the electronic wrist watches were also
manufactured, which had LED display. Electronic wrist watches could
indicate the time but for a shorter period since the LEDs consumed too
much power. Then, properties of liquid crystals were used under the
influence of electric field and pass light with unidirectional
polarization. Light was supplied from external source between two
polarizers and the light is absorbed by the system polarizer – liquid
crystal – polarizer – reflector. If the electrical field is present,
then the light becomes dark and display element is formed. As a result
of this, energy consumption was reduced significantly and battery
replacement takes place infrequently. As a rule, a micro controller is
in-built in contemporary electronic clocks and clocks are manufactured
with many service functions (alarms, melodies, calendars etc) but the
micro controller continues to count the oscillation periods of the
same quartz crystal. Electronic clocks are also available, which are
based on principle of frequency count of feeding circuit. In many
countries, very rigid requirements are applicable to stability of
frequency. During load fluctuations, frequency can vary and accuracy
of such clocks is not considered sufficient, even though, accuracy is
sufficient for many a people. |
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New York city has several public clocks which need regular winding to be kept on time. Clock Tower Building, City Hall, and other historical buildings all have old mechanical clocks, which have been wound for decades by Marvin Schneider, the city's official clock-watcher. He says winding these clocks feels like being in an entirely different century, plus there's a fabulous view on the city from the top.
