What is Combination lock?
[[File:Masterpadlock.jpg|thumb|right|A mechanical combination padlock]] A '''combination lock''' is a lock that is opened with a set of secret numbers instead of a [[key]]. Mechanical combination locks usually have a dial that is rotated to three different numbers (four numbers on some safe locks) to open the lock. Electronic combination locks usually have a keypad where the combination can be entered like a telephone number. == Mechanical combination lock == The mechanical combination lock usually has three discs inside. The last disc is connected directly to the dial, and a notch on this disc rotates the second disc. A notch on the second disc in turn rotates the first disc. The lock is usually opened by [[Rotation|rotating]] the dial [[clockwise]] to the first number, counterclockwise past the first number and to the second number, and clockwise to the third number (some locks use the reverse directions, and most safe locks require a return to 0 after entering the combination). This type of lock is popular on [[Safe (container)|safes]] and [[padlock]]s. It is available for entry doors, but is not popular due to the amount of time required to enter the combination. The combination is usually set at the factory and can not be changed easily (if at all). [[File:Electronic lock with number pad.jpg|thumb|right|An electronic keypad combination lock]] == Electronic keypad lock == The electronic combination lock uses a keypad that looks similar to a telephone keypad. The combination is entered one number at a time, like a telephone number. When the number is entered, a motor opens the lock. This type of lock is popular on safes and doors, but is almost never seen on padlocks. These locks require [[Battery|batteries]] or another source of electricity. There is sometimes a key backup in case the batteries die or the electronics fail. Most safe locks do not have a key backup, as a key backup can be [[Lock picking|picked]]. Most electronic locks allow the user to set the combination. == Advantages == Combination locks