UL 768 is a security rating from Underwriters Laboratories that provides a barometer for the security of a combination lock. Combination locks tested are primarily used on security containers such as safes and vaults. This standard addresses various methods of manipulation and decoding of the combination sequence but does not test against forced entry methods. UL768 provides three types of ratings:
- Group 2
- Locks that have a moderate degree of resistance to unauthorized opening.
- Group 1
- Locks that have a high degree of resistance to unauthorized opening. When compared with Group 2 locks, Group 1 locks provide advanced mechanisms to combat manipulation.
- Group 1R
- Locks that have a high degree of resistance to unauthorized opening. Group 1R locks include resistance to radiological attacks.
- drive cam
- The component that engages tumblers and extends or retracts the bolt during normal use.
- drive pin
- The component on each tumbler that actuates an adjacent tumbler.
- The part of the lever that falls or fits into the tumbler gates, allowing the lever to interface with the drive cam.
- The portion of each tumbler that defines a correct combination and is engaged by the fence.
- The component that retracts the bolt and (usuallly) holds the fence.
- tumbler pack
- All components included in tumblers, such as the wheels, flys, washers, springs, and rings.
- tumbler post
- The component around which the tumblers rotate.
- tumbler, tumbler wheel
- Refers to a wheel in a combination lock that has a gate and drive pin.
General Construction and Operating Requirements
- Locks shall allow at least 1,000,000 different combinations.
- The lever shall fit snugly on the post and shall be secured tightly. The fence shall be perpendicular to the plane of the tumblers.
- Clearance between the fence face and the tumbler wheels shall not be less that 0.025" (0.64 mm) when the bolt lever is raised by means of a driver cam, and not less than 0.015" (0.38 mm) when the bolt lever is raised by means other than the driver cam.
- Tumblers shall be placed at right angles to the tumbler post.
- The lock shall operate properly when the correct combination is entered.
Manipulation Resistance Tests
- Combination wheels are set at various combinations to ensure the lock will operate normally but will not open with the dial turned beyond the acceptable tolerances.
- Tolerances for a three-number wheel lock are 1.25 dial graduations on either side of the correct number.
- Tolerances for a four-number wheel lock are 1.50 dial graduations on either side of the correct number.
- Resists against manipulation and unauthorized opening for 20 hours.
- The time specified above man be one man working for 20 hours, two men working for 10 hours, and so on. Lock experts may be called upon to participate in these tests.
- Manipulation protection shall include advanced features not found in conventional designs.
- Manipulation tests shall include:
- Expert manipulation techniques
- Walking the tumblers
- Feeling the tumbler gates
- Sighting variations on the dial
- Any other techniques developed during testing
- Expert manipulation techniques
- The weight of instruments or detection devices used in tests will not exceed 50 pounds (22.7 kg).
- Tolerances for a three-number wheel lock are 1.00 dial graduations on either side of the correct number.
- Tolerances for a four-number wheel lock are 1.25 dial graduations on either side of the correct number.
- Punching of a Group 1 lock shall result in the lock bolt becoming immobilized by mechanical means.
- Immobilization is not required in locks where punching does not defeat the locking action.
- Compliant with all Group 1 requirements.
- Secure against radiological attacks for 20 hours with a radioactive source not exceeding the equivalent of 10 curies of cobalt-60 at a 30" (762 mm) distance.
UL 768 rated locks
- See UL 768 locks