Abstract: A signalling device is provided having a plurality of differently colored light modules stacked one above the other than function properly regardless of arrangement order of the light modules within the signalling device. The signalling device includes a signal bus having a plurality of channels that extends through each light module. Each channel carries a unique status signal to one light module. Each light module is connected to and identified by a different channel, thus enabling the light modules to be arranged in any order and still function properly. One or all cover plates on each light module may be removed without requiring any light module to be removed from the signalling device. This feature enables both the light modules to be serviced while retaining their color identity and the color of the cover plates to be changed without requiring any light modules to be removed from the signalling device in either situation. The signalling device is quickly assembled with dilating rivets.

Abstract: A control unit is connected, via a data bus, to a plurality of remote field controllers, each of which is in turn connected to a motor starter and status contacts of a respective valve or pump. Binary codes are communicated between the control unit and field controllers to convey status information, regarding a valve or pump, to the control unit. Likewise, command codes are conveyed from the control unit to a pump or valve to effect a selected operation.