The National Instruments GPIB-120B is a GPIB Bus Expander and Isolator, widely recognized by part numbers 779651-01, 779651-04, 779651-06, and 779651-07. This device is engineered for complete compatibility with IEEE 488.1 and IEEE 488.2 standards, allowing users to expand their GPIB bus to connect as many as 28 devices in various test and measurement environments. The GPIB-120B provides exceptional isolation capabilities, offering up to 2,500 VDC of non-continuous isolation between GPIB ports and the power supply, effectively mitigating induced common-mode and ground loop noise. This isolation feature ensures reliable communication between instruments and the IEEE 488 bus controller.

The expander facilitates bidirectional expansion of GPIB system devices, accommodating talkers, listeners, and controllers on either side. Functionally transparent, the GPIB-120B allows existing GPIB control and communication programs to operate seamlessly in both standard and expanded configurations. It supports two data transfer modes: buffered mode with transfer rates up to 1.2 MB/s and unbuffered mode up to 450 kB/s, with unbuffered mode set as the default. Users can easily switch between operating modes using the toggle switch located on the rear of the device. The unit incorporates eight data lines and three hardware handshake lines for comprehensive communication capabilities. Compactly designed with dimensions of 6.30 by 3.68 by 1.24 inches and weighing 8.64 ounces, the GPIB-120B is an indispensable component for enhancing GPIB system functionality. A user manual and maintenance guide are available for download, and inquiries for pricing should be directed to a sales representative.