The VLBA can record data in VLBA and Mark III formats. Characteristics of observations recorded in VLBA format are described in Section 5 and elsewhere in this document. Mark III observations are limited to that format's 4-MHz maximum BB channel bandwidth and 1-bit sampling, and to the VLBA's 8-BBC complement. Mark IV (Whitney 1995) systems are currently being checked out world-wide. Although the VLBA cannot record Mark IV format as such, there is a high degree of compatibility between Mark IV and VLBA formats. Section 18.1 provides further information regarding Mark IV projects involving the VLBA and/or its correlator. The VLBA cannot record in Mark II format, the Japanese K4 format, or the Canadian S2 format.