Trapped key interlocking system

Ensuring the safety of maintenance personnel and visitors at the Lovell radio telescope at Jodrel Bank is now a lot easier since the installation of a special trapped key interlocking system supplied by Sigma Controls. Periodically, maintenanace has to be performed on the dish. At other times, visitors are allowed onto the surface of the dish. Access is via two towers, both of which have doors to a common gantry. The dish pivots between the towers and when it is pointing towards the zenith, the gantry is in line and the dish can be walked upon. However, when the dish is tracking, access is totally prohibited. To meet the safety interlocking requirements, the Sigma trapped key interlocking system was preferred over other systems because it was able to handle the degree of complexity.