| Summary: | In this paper, the researches and the application of manhole over as well as the existing problems have been described. The mechanical security code manhole cover with the built-in locking mechanism has been designed. The locking mechanism can withstand the muddy water immersion test, the password design test, the low temperature alternating cycle test, the failure load test and the vibration test. The manhole cover is equipped with an electric key and a mechanical key. The electric key automatically opens the code lock by receiving the password. The mechanical key demands to manually adjust the dial to open the code lock. The key and the password are respectively managed by different people.
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