1953: diode plug-in unit and the IBM 650
Functionality
Semiconductor diode in the reverse direction
If the voltage is applied in the way that the negative pole is connected to the p-type semiconductor material and the positive pole to the n- semiconductor material, so the atoms move by means of attraction to the diverse charged poles and nurture the junction between the materials, so there is no free moving charges. Conclusion: There is no current flowing.

dt.: Anschluss = connector
dt.: kein Elektronenfluss = no electron flow
Semiconductor diode in conductiong direction
If the connections biased the other way, then move the atoms towards junction - there is an exchange of electrons. Conclusion: The current flows.

dt.: Anschluss = connector
dt.: Elektronenfluss = electron flow
Advantages of diode
- Halved space and energy consumption
- Produced waste heat greatly reduced