The GBT IF/LO system consists of the electronic subsystems and transmission lines used to connect receiver front-end outputs with data acquisition backends. The IF chain accepts an IF signal in the 1-8 GHz frequency range from each front-end, and converts output IF signals at frequencies appropriate for the various backends. Included are frequency synthesizers and other components of the local oscillator (LO) system, whose operation is intertwined with that of the mixers incorporated in the receiver front-ends, and in frequency converters in the common IF chain. Unlike other systems of the GBT the IF/LO system has equipment located on the telescope as well as the Jansky Lab.