PCALXB1 and PCALXB2 determine what the pulse cal detectors measure. There are 16 pulse cal detectors in each formatter and 1 formatter at each VLBA station. (FOR NOW, THERE ARE ONLY 8 DETECTORS AT EACH STATION) Each detector can process two bit streams. In each bit stream, either counts of bits can be determined (PCALFR1=0) or a pulse cal tone can be detected. If the two bit streams are from the same (2 bit) channel, and the frequency is the same for both detectors (PCALFR1 and PCALFR2 the same), the results will be combined for a single measured amplitude and phase. The arguments are treated as character strings. They begin with a letter indicating whether to look at the sign (S) or the magnitude (M) bit. The letter is followed by a number to indicate the channel from which the bits are to come. PCALXB1 specifies the source of the first bit stream for each detector, while PCALXB2 specifies the source of the second bit stream. ``Channel number'' means the same quantity that is used as the index for most setup parameters. A detector can be turned off by specifying 'off'.
Most users should not need to worry about setting the pcal detection parameters. SCHED defaults to a reasonable set which is described in the section on PCALFR1 and PCALFR2.