The Multiplier and Accumulator (MAC) is, hardware wise, the most complex subsystem of the correlator. The MAC takes the FFT outputs computes the cross and self products and accumulates them for a maximum of 128 ms and a minimum of 4 ms. A schematic of the configuration of the multipliers is shown in Fig 25.5. Each MAC unit consists of 256 accumulators. The MAC can be configured in several different modes. As described in more detail below this flexibility allows the GMRT corrrelator to be used to make a wide variety of observations. Data from the MAC unit is read out by the Data Acquisition System (DAS) using a special purpose add on card on a PC (see Chapter 26 for more details).