Index of cooperation

In telecommunication, the term index of cooperation has the following meanings:

1. In facsimile, the product of the total line length and the number of lines per unit length, divided by π.

2. For rotating devices, the product of the drum diameter and the number of lines per unit length. Synonyms: diametral index of cooperation, international index of cooperation.

Source: from Federal Standard 1037C and from MIL-STD-188