A system for controlling drilling unit apparatus includes a plurality of drilling unit apparatus each operated by a corresponding controller. Any one or more of the controllers is in signal communication with either or both of (i) at least one sensor that generates a signal related to an operating condition of the drilling unit apparatus and (ii) at least one other of the controllers to accept as input therefrom a signal related to an operating state of the corresponding drilling unit apparatus. A plurality of time reference signal receivers is each in signal communication with a corresponding controller. An absolute time reference signal transmitter is in signal communication with each time reference signal receiver such that any one or more of the controllers operates its respective drilling apparatus in response to either or both of (i) the sensor signal and (ii) the signal from the at least one other controller.