Abstract: A machine is controlled by a system which has a pair of programmable controllers connected in tandem. One controller operates in the active mode governing the operation of the machine, while the other controller is in a backup mode able to assume control of the machine should the active controller fail. Each programmable controller has a backup module through which the two controllers are connected. In order to determine which controller is to be active upon power up, each backup module has an input means for receiving a first active mode request signal from another programmable controller. A means is provided to produce a tie breaker signal at one backup module which indicates that its programmable controller is to operate in the active mode when both programmable controllers simultaneously desire to operate in the active mode.

Abstract: Composite structural timber which is reinforced with deformed metal bars. The timber comprises a plurality of wooden laminations bonded together by a resin adhesive. There are at least two longitudinally extending metal bars. One bar is located near one longitudinal edge of the timber and the other is located near the other longitudinal edge. The composite structure provides superior load carrying capacity and reduction in deflection under a given load. The main use is as structural timber beams and posts.