Firmware version 1.42 Build 10a is for DBT-120 Revisions A1, A2,B1, B2, and B3. These revisions use Registry Security,which means that you have to enter a security code.

Firmware version 1.42 Build 10 is for DBT-120 Revision B4 andabove. Those revisions use Device Security, which meansthat you do not have to enter a security code because it isbuilt-in to the device.