The vault itself was protected by a dual lock system: a combination and a key lock, and two feet of reinforced steel.
保险库采用密码加钥匙的双重保护系统，并使用厚达两英尺的强化钢板。
2
Taking dual chaotic inter-perturbed system as sequence key generator, an improved quantization method for converting chaotic sequence to binary sequence was put forward.
以双混沌互扰系统作为序列密钥发生器，提出一种改进的二值序列量化方法。
3
How develop the unemployment's this dual character finally to the positive sense of the economical movement, the key measure is to establish an effective unemployment safeguard system.