Input threshold DC maximum. It is a read-write node. The value of this node is 'OCTET STRING', it is used to describe a float value. So this string should fit the following rule: 1. This string should be terminated by '\0'; 2. Every characters should be number or radix point; 3. The radix point should occur only once, and it should not be the first or the last character of the string. It should be smaller than 57.0V and larger than 55.0V.