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This is a trapped-key interlock on the door of an electrical switchgear cabinet. It is attached with one-way security screws to discourage casual removal, which would defeat the interlock scheme. Trapped-key interlocking utilizes locks and keys for sequential control of equipment and machinery to ensure safe operation. Trapped-key interlocks ...
The key will not turn unless the remaining keys are put back in place. Trapped key interlock transfer block. Another example is an electric kiln. To prevent access to the inside of an electric kiln, a trapped key system may be used to interlock a disconnecting switch and the kiln door. While the switch is turned on, the key is held by the ...
Groundframe, with the two rightmost levers locked by Annett's key. In British, Australian, French, and Swiss railway signalling, an Annett's key is a form of trapped-key interlocking that locks levers or other items of signalling apparatus, thereby serving as a portable form of interlocking.
These require a simple key or tool to operate, and thus discourage casual or accidental operation of the switch. [3] [4] In some devices, the switch is built into a keyed lock mechanism, which prevents unauthorized use of the device. In this type of vandal-proof system, when the key is turned in the lock, the user can turn the equipment on.
To help ensure safe operation sequences of switchgear, trapped-key interlocking provides predefined scenarios of operation. For example, if only one of two sources of supply are permitted to be connected at a given time, the interlock scheme may require that the first switch must be opened to release a key that will allow closing the second switch.
In high-voltage or complex systems, these locks may be part of a trapped-key interlock system to ensure proper sequence of operation. In some designs, the disconnector has the additional ability to earth the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits that inter-connect power distribution ...
The Ternkey System ("Token Exchange using Random Numbers" system) is a hybrid between conventional token working and internet technology. Conventional "trapped key" pin tumbler locks (held in fixed position by solenoids ) are mounted in key-release units set up at each end of controlled single line.
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