This is a DC gear motor with encoder, all metal gear to provide high strength and stability. It has an encoder to help users adjust the speed. The gear motor has a large torque, low loudness and easy to use. Besides, the encoder on this module has two outputs: output_A and output_B, to monitor the motor speed and direction of rotation, so that you can monitor the speed and then to adjust it in a closed-loop control. The encoder output 2 signals with 90 degree phase difference. There will be 334 pulses on each of the signal for a round of the motor, with the rising & falling edge, you can get 334x2x2=1336 signals for a round of the motor, with a interval of 360/1336=0.2694 degree.