The Hoister psi factor is a simple dominant allele, designated as P (dominant) or p (recessive). The effect is not additive; i.e. PP is no more powerful than Pp.
The Levine psi factor is sex-linked (X-chromosome) and dominant. Thus, XX and XY are Normals, while X'X, X'X', and X'Y possess the Levine cluster of abilities. The effect is not additive; i.e. X'X' is not any more powerful than X'X.
The Tenny telepathic power depends on 21 matched genetic factors. These factors are identified as A-Z, excluding O, P, S, X, and Y. A dominant in any ten through thirteen factors will result in a weak telepathic sensitivity -- a dominant in fourteen or more factors results in a strong telepathic power. The relationship is not strictly proportional, but varies considerably with experience and training. Most non-Tennys have between five and eight dominant factors.
A complete ("trifamilial") code consists of three parts: the 21 Tenny factors, the Hoister factor, and the Levine factor. It is common to reduce the Tenny portion by recording only the dominant factors.
A + following the code indicates some unusual factors; records at Thank God should be consulted.
Minor Family genes -- i.e. Cooke, Hanson, Luellen, etc. -- are indicated if present, but left off if not.