This read-write attribute, defaulting to disable, configures the OC-3 card as either the primary(priSrc) or secondary(secSrc) source for network clock recovery, valid only when networkClk is selected elsewhere via hcxSyncClkConfigure, and the system permits only one OC-3 card as primary and one as secondary. It lets an administrator designate which optical trunks the headend derives its network timing reference from. For example, an operator setting up clock redundancy would configure one OC-3 card as priSrc and a second, different OC-3 card as secSrc to protect against loss of the primary timing source.