Murphy's [Revised] Laws

 1. All warranty and guarantee clauses become void upon payment of invoice.
 2. Dimensions will always be expressed in the least usable terms, i.e.
    Velocity will be expressed in furlongs per fortnight.
 3. Identical units tested under identical conditions will not be identical in
    the field.
 4. A dropped tool will land where it can do the most damage.  (Also known as
    the law of selective gravitation.
 5. The probability of a dimension being ommitted from a plan or drawing is
    directly proportional to its importance.
 6. Interchangable parts, won't.
 7. Probability of failure of a component, assembly, subsystem or system is
    inversely proportional to ease of repair or replacement.
 8. If a circuit cannot fail, it will.
 9. A fail-safe circuit will destroy others.
10. A transistor protected by a fast-acting fuse will protect the fuse by
    blowing first.
11. A failure will not appear until a unit has passed final inspection.
12. A purchased component or instrument will meet its specs long enough, and
    only long enough, to pass incoming inspection.
13. Firmness of delivery dates is inversely proportional to the tightness of
    the schedule.
14. If a prototype functions perfectly, subsequent production models will
    malfunction.
15. If an obviously defective component is replaced in an instrument with an
    intermittent fault, the fault will reappear after the instrument is
    returned to service.
16. In any given price estimate, cost of equipment will exceed estimate by a
    factor of 3.
17. Manufacturer's spec sheets will be incorrect by a factor of 0.5 to 2.0,
    depending on which multiplier gives the most optimistic value. For
    salesmen's claims these factors will be 0.1 or 10.
18. In specifications, Murphy's law supercedes Ohm's.