The BK Precision DR1DIO Single-Channel Digital I/O and Analog Control Card is designed for use with the 9170 or 9180 Programmable Dual-Range DC Power Supplies (not included). This model is for use with single-channel main units and can be easily installed by the user. This card will upgrade the main unit so that digital I/O and analog control are possible. With the DR1DIO installed, the main unit's output voltage and current can be controlled by either external analog voltage or resistance. By utilizing a 0 to 5 volt external DC voltage source, 0 to 10 volt external DC voltage source, or a 0 to 5 kiloohm variable resistor, the output can be controlled from zero to full scale.