The heart of the Correlator signal path is the correlator itself. The correlator is a specialized supercomputer with custom boards. The correlator does one thing, and it does it extremely well: it performs matrix multiplication.
Once all the data for an observing project is read into the correlator, it begins the process of matrix multiplication. The data of each VLBA site is multiplied against every other VLBA site synchronized by the timing signals that are put on the recording media by the maser. In this manner the raw astronomical image data is built up in the correlator.
After all the matrix multiplication has been performed, the raw data is reformatted for the output media.