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\[[Image: 1GPIB.jpg|thumb|National Instruments GPIB Controller]\]
GPIB controllers monitor and detect activity on the GPIB. When the controller detects a device or instrument about to send a data message, or talk, it connects that talker device, which then broadcasts the message across the bus. Another device on the bus or the controller then assumes the role of the listener and receives that message. [GPIB Controllers|http://volt.ni.com/niwc/gpib/controllers_what_is.jsp GPIB Controllers]
The GPIB consists of one or more interface boards and one or more instruments. The interface boards are GPIB controllers, which govern the flow of information on the bus. They do this by commanding instruments to talk or listen and responding to service requests from devices. There can be more than one GPIB controller on the bus, but only one can be active controller, or Controller-In-Charge (CIC) at any given time. A GPIB controller can pass control of the bus from itself to another controller on the bus, but only one controller (system controller) has ultimate control of the bus. Only the System Controller, usually a GPIB interface, can make itself the CIC by asserting IFC (Interface Clear), one of five GPIB interface managment lines. It is responsible for overall bus management. [GPIB|http://zone.ni.com/devzone/cda/tut/p/id/3387 GPIB]
This model is: ''NI GPIB-USB-HS, GPIB Controller for Hi-Speed USB (unconfirmed if this is the exact one in lab)''