RS-448-4-1980 Standard Test Methods for Electromechanical Switches (Test Methods for Logic (TTL) Level Endurance and Low Level Endurance) (Addendum 4 to RS-448)
"PURPOSE The Logic Level Endurance Test is a measure of the ability of a switch to control electrical loads in which the applied voltage exceeds the melting voltage of the switch contact material and is less than the arcing voltage and arcing current. Electronic logic circuits have defined interface signal voltages. Logic ""0"" is a signal voltage between0 and 0.9 volts. Logic ""1"" is a signal voltage greater than 2.4 volts and less than 5.5 volts."