just this once, then I'am off for vacation
Dozy, Say I develop an intricate and efficient new line in my production shop, it will streamline my production, cut cost, and widen my market. Something I can be proud of.
I pay the enormous development costs, exercise patience, have it installed, and debugged. It has problems, as do all sophisticated technologies, and it goes on line. Some of the problems have to do with training my personnel, so an expensive and sophisticated system takes care of that.
It works flawlessly. As it happens, there is a fantastically remote chance it may malfunction, which is acknowledged, and workarounds are installed. The workarounds are not modern, and involve a bypass of the new technology onto the old (left in Place) machine.
There are now two methods of avoiding this remote malfunction.
Step One. Do nothing. The machine has a good chance of self correcting.
ALTERNATE. Cycle THIS LEVER, and the line switches to the old machine which has a phenomenally good record with this remote but systemic problem.
In my business, it is called the CRITICAL PATH. Only in my business, if the Path is lost, no-one dies.