Abstract: A controller for controlling the operation of an automatic machine which includes a number of pneumatically operated devices, for example a machine for blow moulding hollow glass articles, comprises a closed box containing a number of valves each of which is arranged to control one of the pneumatically operated devices of the machine. A first compressed air supply system is connected to the box for supplying compressed air to some only of the valves in the box, the remaining valves being shut-off from this system, and a second compressed air supply system is provided for supplying these remaining valves which are not supplied by the first system. Pressure relief means is also provided for de-pressurising one of the systems so that the valve supplied by this system and the devices which they control become inoperative while the other valves remain pressurised by the other system and accordingly the devices controlled by these other valves remain operative.