By means of the method of descending dimension for establishing inequalities(see theorem 1 and its corollaries), This paper proves a class of inequalities for symmetric functions.

The symmetric ternary current-mode CMOS circuits designed by using this theory not only have simpler circuit structures and correct logic functions, but also can process two-way signal.

Symmetric operators, such as the arithmetic, equality, relational, and bitwise operators, are best defined as ordinary nonmember functions.