I.1 – All warranty and guarantee clauses become void upon payment of invoice

I.2 – Dimensions will always be expressed in the least usable terms. Velocity, for example, will be expresses in furlongs per fortnight

I.3 – Identical units tested under identical conditions will not be identical in the field

I.4 – A dropped tool will land where it can do the most damage. (also known as the law of selective gravitation)

I.5 – The probability of a dimension being omitted from a plan or drawing is directly proportional to its importance

I.6 – Interchangeable parts won’t

I.7 – Probability of failure of a component, assembly, sub-system or system is inversely proportional to ease of repair or replacement

I.8 – If a circuit cannot fail, it will

I.9 – A fail-safe circuit will destroy others

II.1 – An expensive, obsolete transistor protected by a fast acting fuse will protect the fuse by blowing first

II.2 – A failure will never appear until the unit has passed the final inspection and taken by the customer

II.3 – A purchased component or instrument will meet its spec long enough, and only long enough, to pass incoming inspection

II.4 – Manufacturers spec sheets will be incorrect by a factor of 0.5 to 2.0, depending on which multiplier gives the most optimistic value. For salesman’s claims these factors will be 1.0 to 10.0

II.5 – In specifications, Murphy’s Law supercedes Ohm’s