| 摘要 |
A novel way of keeping thieves out of dwellings and other spaces utilizes two interlocked, relatively nested doors which, when so interrelated, are in turn, separately locked as a unit within the door frame. Release from the exterior requires knowledge of a secret system of a push-button control which must be operated in proper sequence. Special, tamper-proof hinges, common to the doors, permit them to be hung in the door frame for separate swinging or movement as a unit. The interlock between the doors is releasable only from the inside and, upon such release, the outer door remains locked until separately released by the occupant.
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