Other controls such as interlocks, timers and limit switches could be added to the circuit. Various interlocks that would automatically shut ventilation valves were disabled. Interlocks and safeguards are mandated to minimize this risk. The scanners' safety requirements include fail-safe controls and multiple overlapping interlocks. Automatic interlocks and 'feeler' relays were used to avoid accidental cross-connections. By physically blocking incorrect operations, valve interlocks enforce such sequences. They control shunting paths and are not fitted with interlocks. Properly designed autoclaves incorporate several additional interlocks for added assurance. Interlocks, shutters, and warning lights are often critical elements of modern commercial installations. Commonly interlocks are added to a control circuit. Enclosure interlocks should be respected and special precautions taken during troubleshooting. These were also responsible for weaponising, systems engineering, aerodynamics, safety interlocks and flight trials. This could be quite dangerous if safety interlocks were not maintained properly. A torpedo tube has a considerable number of interlocks for safety reasons. Analyses of corporate interlocks have found a high degree of interconnectedness amongst large corporations.