Analyzing the resistance characteristics of a p-n junction diode clarifies its behavior. High resistance signifies the diode is "off," operating as an open circuit or non-conducting switch. In this context, resistance measurement determines current flow capability: high resistance blocks current (open switch), while low resistance permits current (closed switch).
Consequently, a p-n junction diode with high resistance functions as an "off" switch, impeding current passage. The diode therefore acts as a switch when resistance between its p and n ends is elevated.