This read-create Integer32 encodes the physical position - frame, slot, and port - of the clock source feeding a clock-input entry, packing the frame ID, slot ID, and port ID into successive bytes of the value; it is set to NULL-ULONG when the source isn't a system-line clock. Admins set this value when configuring a system-line clock source to point the clock manager at the exact physical port supplying timing. For example, an admin wiring frame 1, slot 2, port 3 as the timing source would encode those three byte values into hwClkInPostion.