In a target tracking and acquisition system under the control of a human operator, said system having a sensor and display switchable from a low to a high magnification, operator controllable means for switching from said low to said high magnification, and a controller having means for providing proportional control of the sensor, said controller also having a rate-aiding parallel integrator constituting means for providing integral control of the sensor and in conjunction with the proportional control means of the controller constituting means for providing proportional-plus-integral control, the improvement comprising:
- means for initializing the integrator during low magnification of the sensor and display and means for automatically and instantaneously switching from proportional to proportional-plus-integral control of the sensor when the magnification of the sensor and display is switched from low to high;
- said controller including means for providing proportional control of the sensor at a high gain and means for providing proportional control of the sensor at a low gain, wherein the operator controllable switching means includes means for changing the gain of the proportional control from high to low when the magnification of the sensor and display is increased from low to high to compensate therefor, further including electronic switching means governed by the operator controllable switching means for supplying the integrator with a high gain proportional signal and for configuring the integrator as a continuous sampler when the sensor and display are at low magnification thereby to initialize the integrator for operation of the system at high sensor and display magnification so that control transients do not occur upon switchover from low to high magnification.