The security door key downstairs in the house, with A, B. Because the family rented the house, so, b

At present, according to the "Mechanical Anti-theft Lock" standard issued by the public security department in 2015, the anti-theft door is divided into three levels, A-level lock, B-level lock, and C-level lock, and the anti-theft performance from A-level to C-level is getting higher and higher. The differences between Class A, B, and C keys are as follows: >>>More

How to use the ab key:

After getting the house, the homeowner will get the key to the door, and now generally there will be two types of keys, A and B, and the property will explain the specific distinction and use of these two keys. For example, it will be explained that the A key is used for the decoration of the house, and the B key is used by the owner after the decoration, when the house is decorated and the owner is qualified, the house should take back the A key in time, and then use the B key to insert the lock cylinder and rotate it once or then rotate it in the opposite direction, and the A key will automatically become invalid. >>>More

This is also more common now. It is a quality problem that belongs to the lock. The solution is to replace the door lock. Don't say AB keys. Even the high-end three-color keys have the same situation. It is recommended that you replace the Class B anti-theft lock.

Then you'd better change the lock, so that it is a kind of protection for both parties.

The marble chamber in the pit corresponding to the different depths of the A and B keys has a special structure and is equipped with a 1mm steel ball between the upper and lower marbles. When using the A key, the height of the lower bullet in this marble chamber plus the height of the small steel ball is just flush with the lock cylinder, so the A key can be used to twist the lock cylinder to unlock; When using B key, just can be small steel ball ejected out of the lock cylinder, that is to say, the lower bead and the lock cylinder are flush at this time, so the B key can also be twisted to unlock the lock cylinder (this principle is the same as the child and mother key system), but when the lock cylinder rotates at a certain angle, the small steel ball will be subjected to the effect of the upper spring spring, fall into the blind hole that is cleverly designed on the lock cylinder in advance (this is the difference with the child and mother key system), some people call this small blind hole a trap, very appropriate. The diameter of this blind hole is larger than the small steel ball, but smaller than the diameter of the marble, otherwise the marble will fall and the lock cylinder will be stuck and cannot be unlocked. >>>More