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A time bomb's timing mechanism may be professionally manufactured either separately or as part of the device, or it may be improvised from an ordinary household timer such as a wind-up alarm clock, wrist watch, digital kitchen timer, or notebook computer. The timer can be programmed to count up or count down (usually the latter; as the bomb ...
Sound sample ⓘ An 1860s-era siren. [2] A siren is a loud noise-making device. There are two general types: mechanical and electronic. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire engines.
These devices would detonate the bomb if it was moved in any way. Typically, the safety-arming device used was a clockwork Memopark timer, which armed the bomb up to 60 minutes after it was placed [92] by completing an electrical circuit supplying power to the anti-handling
A similar siren system in Carstairs, Scotland, called the Carstairs Hospital Siren System, uses 9 sirens, 7 of them being Secomak CS8, 1 being a Klaxon GP8 and 1 being Secomak GP12. The hi-lo signal is rarely used since during emergencies, they sound a continuous tone for 8 minutes and in all clear, they sound a long wail, consisting of 30 ...
Hawaii has a statewide system of green painted Federal Signal Modulators and Modulator II sirens throughout the state to warn of tsunamis, volcanic eruptions, bomb threats and any other dangerous emergencies or natural disasters. They are replacing a system of old mechanical Federal Signal sirens, such as Thunderbolts, SD-10s, among others, in ...
The Public Warning System (PWS) is a network of civil defense sirens installed by the Singapore Civil Defence Force on over 2,000 strategic points in Singapore to warn Singaporeans of impending dangers, air raids and atomic bomb blasts. Thus far, the siren network has only been used for occasional public awareness drills, monthly noon chimes ...
The sirens are tested at 1500 on the 3rd of every month. The test comprises the following: [9] 3 minutes of the alert warning (a continuous, stepped, rising tone) 1 minute of silence; 1 minute of the all clear siren (a continuous constant tone) Local volunteers monitor the sirens on test day. [10]
A British air raid siren from the Second World War. All clear is the signal, generally given by an air raid siren, which indicates that an air raid or other hazard has finished and that it is safe for civilians to leave their shelters; it is commonly used in radios as well.