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| | Alarm clock is a special type of clock, which generates sound or light signal at specific time. The basic purpose of such clocks is waking up the owner in the morning. Alarm clock also can be used as “Reminder” or timer.
History:
Alarm clock: Radio receiver with similar adjustment. Graded sticks made of resin mixture and sawdust to which load was tied with threading are used in ancient China as alarm clocks. Stick was ignited, and when it completes burning till thread it falls down on metallic stand.
In ancient Greece, similar devices were used for water clocks.
Mechanical alarm clock was built by American Levi Hutchins in 1787 year. Device used to issue sound signal only at 4:00. French Antoine Redier patented the alarm clock with the provision of setting for any time in 1847.
Firm Westclox in 1908 has offered alarm clock “Big-Ben”. Entire body of clock served as bell in it, due to which sound of alarm clock was loud.
Devices, which will provide reliable wake up of human being, are under development. Basically two problems are trying to solve in them:
How to prevent owner from sleeping again by switching off the alarm clock.
How to wake up ultimate smoothly without pain.
One of such device got Noble prize in 2005.
Mechanical alarm clock
Apart from common clock mechanism, mechanical alarm clock has ringing mechanism, which sets in action by separate spring and acts as per the principle of key doll. This mechanism has two independent interlocks:
Axle of clock wheel has additional disc with notch, connected with additional (“ringing”) arrow. When clock arrow coincides with ringing arrow, projecting part on clock wheel falls in notch, and interlock releases the ringing mechanism.
Second interlock is linked with button and provides switching off of ring any time.
Electro-mechanical alarm clocks use similar mechanism.
Electronic alarm clock
Alarm clock – radio receiver with digital adjustment. Electronic alarm clock could solve the problems, which were not solved by mechanical:
Wake up procedure was improved:
On pressing the button from top of the alarm clock, “Give me sleep” mode starts. 10 minutes break will be given to the owner, after this alarm again gets activated. Alarm clock fully gets switched off with small button, which is not easy to press automatically;
Music instead of ring (melody recorded in memory of alarm clock will be played or radio receiver or player will be switched on);
Gradually ascending ring sound.
Ringing time is set very accurately – up to one minute.
May clocks provide setting of two or more alarms at a time.
Mechanical alarm may ring maximum after 12 hour after setting. For electronic alarm clock, this duration is increased up to 24 hours.
Alarm is available practically in all electronic clocks. Alarm function is frequently included in players, Television, radio receivers, mobile phones etc.
Recommendations regarding selection of alarm clock
Alarm clock is inexpensive, however unfortunately purchased alarm clock may become waste. These recommendations will help you in selection of suitable.
Be sure in sufficient sound level so to reliably wake up you. Look for suitable for you melody of sound. Think whether you require or not increasing sound.
If you are buying electronic alarm clock for basic use (wake up in the morning), ideal algorithm is: for wake up in the morning, evening you switch on; when you press the button on top of alarm clock, it gives some calm time; finally alarm clock stops by pressing the small button; if for longtime no body reacts on alarm, then it gets switched off automatically. Such alarm will not disturb neighbors, when you are in journey, and will not wake you up when there is a possibility to sleeve more.
If you are buying mechanical or electro mechanical alarm clock, then be sure that it ticks calmly. Alarm clock based on cheap mechanism ticking once in second may disturb you in getting sleep. This is related to any clock located in bedroom.
If the alarm clock is combined with radio, speaker of switched off receiver should not generate any sounds even small. Any sound – feature of non-reliable scheme, there is a risk that they may develop to calm but persistent «mumble».
For alarm clock working with current, reserve battery is required and cheap spare alarm also required. Every if power fails, time should not be stopped.
If alarm clock works on battery, do not replace it with rechargeable battery. Recharge battery works for longtime, but at the same time due to high current of self-discharge requires frequent charging.
Alarm clock in cinematography
Cinema “Groundhog Day” - a scene was to be shot, where irritated Phil breaks the alarm clock into pieces but the shot was not cleared as Phil could not break it. Due to impact of Murray, clock developed cracks and as a result, the shooting team was forced to hit the clock with hammer. In spite of this (shown in the film), the clock did not stop ringing.
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