There is a set of warning lights on the Control Desk which signal major changes of state and/or situations which could endanger the telescope hardware. Alarms can be of various types and upon no account should any be ignored. You will be unable to ignore an alarm anyway because, when an alarm occurs and a warning light comes on, the system also trips a relay which sounds a high-pitched, loud and very irritating whistle. A typical contingency (which we hope will never occur) would be a loss of oil pressure in the hydrostatic telescope bearing.
A failure of the air conditioning system will activate an alarm in the Air-Conditioning Plant room located outside the Control Room on the roof.
Normally, the Telescope Operator or Duty Technician will cope with these situations. Nevertheless, just in case, there is an emergency STOP button on the top-lefthand side of the Control Desk. Actually, certain fault conditions are best handled by using the emergency stop, such as encoder or CAMAC failures, which can cause a run away motion of the telescope.