A Geometric Interpretation of Diagnostic Data from a Digital Machine: Based on a Study of the Morris, Illinois Electronic Central Office

To identify a malfunction is always difficult. The great size, complexity, and speed of modern digital machines render this difficulty severe. An age-old method is to observe the symptoms and deduce their cause. For larger machines, this is exceedingly impractical. A familiar aid is the use of tests. The record of tests passed and tests failed provides many more clues to the trouble. However, even the use 1299 1300 T H E B E L L SYSTEM TECHNICAL J O U R N A L , OCTOBER 1966 of tests does not avoid time consuming analysis by a highly trained expert, which is slow and expensive. One very successful and ingenious approach to alleviating this difficulty (proposed by Werner Ulrich) is to make a large dictionary listing many malfunctions with corresponding test results. For each of many known malfunctions, we obtain a pattern of 0's and l ' s which indicate the test results. For example: Test Number Result 1 2 3 4 5 00 10 1 6 7 8 1 0 0 ···.