  The large size of the time ordered data of cosmic microwave background
experiments presents challenges for mission planning and data analysis. These
issues are particularly significant for Antarctica- and space-based
experiments, which depend on satellite links to transmit data. We explore the
viability of reducing the time ordered data to few bit numbers to address these
challenges. Unlike lossless compression, few bit digitisation introduces
additional noise into the data. We present a set of one, two, and three bit
digitisation schemes and measure the increase in noise in the cosmic microwave
background temperature and polarisation power spectra. The digitisation noise
is independent of angular scale and is well-described as a constant percentage
of the original detector noise. Three bit digitisation increases the map noise
level by < 2%, while reducing the data volume by a factor of ten relative to
32-bit floats. Extreme digitisation is a promising strategy for upcoming
experiments.
