Transmission circuit, electronic control unit, and vehicle

A transmission circuit, comprising:

• a first terminal configured so that a first voltage is applied thereto;
• a second terminal;
• a third terminal;
• a fourth terminal configured so that a second voltage lower than the first voltage is applied thereto;
• a first variable resistor portion provided between the first terminal and the second terminal and configured to vary in resistance value;
• a first current restriction portion provided between the first terminal and the second terminal and configured to restrict a current flowing from the first terminal to the second terminal;
• a second variable resistor portion provided between the third terminal and the fourth terminal and configured to vary in resistance value;
• a second current restriction portion provided between the third terminal and the fourth terminal and configured to restrict a current flowing from the third terminal to the fourth terminal;
• and
• a control portion configured to control, based on transmission data, the respective resistance values of the first variable resistor portion and the second variable resistor portion,
• wherein
• the first current restriction portion and the second current restriction portion each serve as a constant current source.