An example test system includes a test head, and a device interface board (DIB) configured to connect to the test head. The DIB is for holding devices under test (DUTs). The DIB includes electrical conductors for transmitting electrical signals between the DUTs and the test head. Servers are programmed to function as test instruments. The servers are external to, and remote from, the test head and are configured to communicate signals over fiber optic cables with the test head. The signals include serial signals.