This object configures whether a DS1/E1 interface derives its transmit clock using SRTS (Synchronous Residual Time Stamp) or adaptive clock recovery, both methods for reconstructing timing over a packet network. An administrator sets this based on the clocking architecture of the circuit, choosing adaptive when no common network clock reference is available. For example, setting qbdsx1ClockMode to adaptive(3) on a T1 circuit backhauled over an IP network lets the interface derive timing from the incoming packet stream rather than requiring an external clock source.