The JSB4915 is a USB data acquisition module designed to track up to 5 quadrature encoders as differential inputs. Each of the five channels has a dedicated 24-bit real time 1MHz counter. The module provides 4 channels of 10 bit 20 kHz PWM (pulse width modulation).  In addition there is 8 digital inputs and 8 darlington (DS2003) digital outputs. The JSB4915 supports both indexed and non-indexed encoders in a X1, X2 or X4 count mode.  It provides independent bi-directional counters for each of the encoders at a rate up to 1MHz.  Each module has an unique serial number string which allows multiple USB devices to be controlled by the host USB controller as individual devices. The module supports USB 2.0 or 1.1 interface to the Host PC.