This is a mask which indicates which tests from the 'prtGenTestCmd' list are allowed for the selected port. If a specific test is allowed, its respective bit will be SET in the mask : TEST BIT localLoop 1 remoteLoop 2 bert 3 plb 4 inband 5 prbs 8 loop2-v54 (RLB) 9 loop3-v54 (LLB) 10 Tone injection 13 Tx-plb 14 Tx-llb 15 DTE loop (HSSI) 16 HDSL-Tx-Inband 20 HDSL-Rx-Inband 21 Monitor 22 (test port) User Line Loopback 23 Rem-Loop-on-Rem-Unit 25 LBBD 26 LB1 27 LB2 28 BERT-on-Rem-Unit 29 TS Remote Loop 30 LLB-on-Rem-Unit 31 e.g : If the return value is 3 -> 0000000000000011 -> Bits 1 & 2 are set -> the allowed tests are : local-loop remote-loop