Jinx clear.net.nz> writes: > there are many household appliances, such as stoves, heaters, lamps > etc, that run on exactly the same mains as found in a hospital and > quite capable of delivering no less a lethal belt than a faulty heart The short version: Medical grade devices (esp. electrical) are expected to be used with 'open' bodies (contact wounds etc). That lowers the electrical resistance of the body by removing the very high insulation provided by the skin. The result is that the current needed to kill someone or cause pain is much lower than 'with' skin, by a ratio of 1000:1 or so, and then there are inter-operability issues between types of equipment. The leakage and grounding (and not grounding - several devices are expected to be floating wrt. ground) standards for medical and hospital grade equipment reflect this. Then they must not create ignition sources (ether and some anesthetic gases ignite in air under 200 degrees C - so does Hydrogen if a catalyst is present - I heard cigarette ashes contain such ...), plus there are power devices (like defibrillators) which create immense input disturbances that should not destroy circuits and also not create leakage that may cause trouble, even if they fry the circuits. This is more or less the electrical side. The regulation side is very complex as someone else observed. Like everything else, there is a price tag on regulation (testing and compliance) for such devices, and it is hefty. I heard that it is unclear whether weapon system electronics or medical electronics are more expensive to certify (this could be funny if it would not be sad). Peter -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist