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Figure 1: Ancient Egyptian lock Figure 2: Contemporary version of the Yale lock (Left) All pins lifted to proper height by correct key, which can be turned to open lock, and (right) pins lifted to incorrect height by wrong key, lock will not open Figure 3: Warded lock and key Figure 4: Barron tumbler lock, 1778 Figure 5: Bramah lock, 1784 Figure 6: Combination safe lock The lock cannot be opened until the slots on the three wheels are in line; movement of the dial is transmitted to each wheel by a system of pins (in practice much shorter than shown), arms, and studs cylinder lock
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Over the years, locks have been constructed with many specialized functions. Some have been designed to resist being blown open, others to shoot or stab intruders or seize their hands. Locks have been made that can be opened or closed by different keys but can be unlocked only by the key that closed them. So-called unpickable locks are usually devised to prevent a thief from exploring the positions of the lock parts from the keyhole or from sensing with his picking tool slight changes of resistance when pressure is applied to the bolt. The basic types, however, remain the Bramah, ...(100 of 2226 words)

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