Selects the test bit pattern the BERT engine transmits and checks, such as a pseudo-random 2^11-1 or 2^23-1 sequence, all-ones, all-zeroes, or an alternating 1-0 pattern. The DESCRIPTION is empty in this MIB, so this reading is inferred from the object name and its enumerated pattern list, which matches standard ITU/ANSI BERT test patterns, rather than vendor text. An admin testing a new circuit for jitter sensitivity might select alternatingOneZero(7) since that pattern stresses timing recovery.