Each bit corresponds to a test item. The various bit positions are: Bit 0: vac, test AC voltage Bit 1: vdctest, DC voltage Bit 2: rload, test load resistance Bit 3: riso, test isolation resistance Bit 4: cap, test capacitor Bit 5: ren, test REN value Bit 6: ring, test ring voltage Bit 7: metering, test metering voltage Bit 8: dialtone, test dialtone Bit 9: digit, test digit Bit 10: roh, test roh Bit 11: loop, test loop and battery conditions Bit 12: rrev, test reverse polarity resistance.