A diode bridge makes use of four diodes in a bridge arrangement to attain full-wave rectification. This is more commonly known as a bridge rectifier. Its output is rectified DC from an AC source and the polarity is the same irregardless of the polarity of the AC input. The resulting output waveform is not true DC, it contains a ripple. When used in power supplies to rectify the incoming AC the output waveform must be handled by the rest of the power supply circuitry to reduce its ripple thus making a clean DC output. Another application would be reverse polarity protection in the input of a battery circuit to make sure no damage would occur if a battery was inserted into a device with the wrong polarity.