A first level of control over operation of slave Digitally Controlled Frequency Selectors (DCFSs), such as DCOs or DDSs, may occur by periodic transmission of control words from the master clock to the slave clocks. To allow enhanced control over the output of the slave clocks, the frequency of the local oscillator used to generate the synthesized output of the master clock may also be conveyed to the slave clocks to allow a second level of control to take place. The second level of control allows the local oscillators at the slave clocks to lock onto the frequency of the master local oscillator to thereby allow the slave local oscillators to operate the slave DCFSs using the same local oscillator frequency. The first level of control synchronizes operation of the DCFSs while the second level control prevents instabilities in the local oscillators from causing long term drift between the slave and master clock outputs. Timestamps may be used to synchronize the master and slave local oscillators.