Expending on your correction, there are some appropriate diagrams in this article: * https://www.allaboutcircuits.com/textbook/digital/chpt-3/logic-signal-volt

Expending on your correction, there are some appropriate diagrams in this article: * https://www.allaboutcircuits.com/textbook/digital/chpt-3/logic-signal-voltage-levels/ https://www.allaboutcircuits.com/textbook/digital/chpt-3/log... Any practical binary logic scheme is going to have an undefined zone in the middle because the gain of the devices used for the logic is not infinite and there would be problems caused if the gain was too high.