An infusion device for a syringe includes a ratcheted stepper motor driven intermittently under the control of a control circuit to advance a syringe plunger driver. Different speeds are determined by the detected size of the syringe in the device. A clutch assembly disengageably connects the plunger driver to a drive belt driven by the stepper motor.A connector for a tubing set has a syringe-connect portion located in a recess of the connector, and cooperates with a force sensor in the device to detect occlusions. The connector has annular projecting portions with parallel, spaced apart actuating surfaces for engagement of the force sensor in either of two positions of the connector in the device. The connector is adapted to indicate to a sensor in which position it is located.