Interlock (engineering)
An interlock is a feature that makes the state of two mechanisms or functions mutually dependent.
Interlocks may include sophisticated elements such as curtains of infrared beams, photodetectors, simple switches, and locks.
Trapped-key interlocking is a method of ensuring safety in industrial environments by forcing the operator through a predetermined sequence using a defined selection of keys, locks and switches.
After the control or power has been isolated, a key is released that can be used to grant access to individual or multiple doors.
In modern days, most cars have an anti-theft feature that restricts the turning of the steering wheel if the key is not inserted in the ignition.
A major problem in engineering operator safety is the tendency of operators to ignore safety precautions or even outright disabling forced interlocks due to work pressure and other factors.
In order to safely transfer the power source from a generator (and back to the main), a safety interlock is often employed.
An interlock device is designed to allow a generator to provide backup power in such a way that it (a) prevents main and generator power to be connected at the same time, and (b) allows circuit breakers to operate normally without interference in the event of an overload condition.
Some also allow for the use of padlocks to prevent someone from accidentally activating the main power system without authorization.
[4] In high-security buildings, access control systems are sometimes set up so that ability to open one door requires another one to be closed first.
One example of a hazard is if a software program loads data from the system bus and calls for use of that data in the following cycle in a system in which loads take multiple cycles (a load-to-use hazard).
