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To: Boplicity who wrote (1289)	3/8/2000 11:31:00 AM
From: Dinesh	Read Replies (1) \| Respond to of 3076

Greg Can you possibly post where it states the topology as serial ? I would seriously doubt this since the drawbacks are so obvious. Particularly in industrial arena. Lon supports wireless connectivity. This should help a ton. Regards Dinesh

To: Boplicity who wrote (1289)	3/9/2000 2:36:00 AM
From: KW Wingman	Read Replies (2) \| Respond to of 3076

The process control networks I am best familiar with, are used in very critical and potentially hazardous applications. A good example of this is a dynamically positioned offshore semisubmersible. The most advanced type of this drilling rig can drill an oil well in water depths up to 10000 ft. Dual or Triple Redundant Computerized Process control systems monitor thousand of sensors and control or monitor nearly everything on the vessel. - Control of ship or rig position on the ocean so that the vessel stays directly over the drill site +- 1/2% of water depth 99% of the time. - Total Power management, engine/generator, electrical switchboard control and distribution. Load shedding as required in event of engine or electrical failure so as not to "lose the load". - Control of ballasting system in four pump rooms. A semisubmersible is somewhat like a drilling rig built on two submarines. - Monitor and control of all kinds of other things on the rig or ship. Yes this network was a serial network on a dual coax on different runs. It had a loop, it was not like a string of serial lights (one out all out). Critical systems also have hard wire back ups and in the case of the ballast system it also had an emergency hardwire backup and if all that failed it still had manual control backup. The following is just my way of pointing out that the old ways may not be the best way: In about 1983, The "Ocean Ranger" semisubmersible sank off of Newfoundland. That rig was very much less complex than the first rig I described. The Ocean Ranger had manual control of the ballast valves as well as a hard wired system and a backup emergency system. The accident was not due to failure of a computer control system because they didn't have such a system. I am not claiming the accident would have been prevented by having such a system either. IMO, the cause was several human errors and lack of proper training of the crew. Critical applications such as this have many redundant features so that failure of any device can occur without a serious problem. The system is designed so that you can burn or destroy whole sections of the network consisting of many devices, and still not have an immediate operational problem. However, loss of redundancy will normally require that you shut down the operation to fix the problem. Technology makes hazardous operations much safer because this redundancy can be installed at a reasonable cost. Todays world, demands this safety. We have no tolerance for screw ups. This makes a big market for anything high tech that will make the plant safer, easier, to operate and understand .