Continuous control is used to produce the correcting variable on controllers using linear output(s).
It typically has 4 to 20mA, 0 to 20mA, 0 to 5V, 0 to 10V or 2 to 10V DC outputs for proportional control in PI, PD or PID modes. On-off control cannot be used with linear outputs.
Continuous control is sometime called Current Proportioning.