The Model 2243 is an optional IEEE-488 interface for the Model 224 Programmable Current Source. This interface adds extra versatility to the Model 224 by allowing the transmission of data and commands over the IEEE-488 bus. The interface provides all the logic necessary to interface the Model 224 to the bus using standard IEEE-488-1978 protocol. Additionally, the Model 2243 incorporates a separate digital I/O port that may be used to interface the Model 224 to other digital instrumentation. Important IEEE-488 interface features include: 1. With the Model 2243 installed, the Model 224 is able to communicate with other instrumentation using the same IEEE-488-1978 standards. 2. Standard IEEE Connector. A standard IEEE-488 connector is available on the rear panel of the instrument for easy connection to the IEEE-488 bus. 3. Simple Primary Address Selection. The primary address of the Model 224 may be easily changed by using the five address switches on the rear panel of the instrument. 4. Digital I/O Port. The interface also includes a digital I/O port which has separate 4 bit input and output connections. Port status may be read and controlled through commands given over the IEEE bus. 5. Programming Versatility. All Model 224 operation is supported by IEEE programming. In addition, numerous other IEEE commands add operating features not available from the front panel.