Mining apparatus

Claim 1

For use in a mining apparatus including a cutting machine and a plurality of roof supports, each having an advance-initiating means responsive to a command signal for controlling the advance of the roof support, arranged side-by-side along a mineral face to be cut by the machine, a control means comprising: (a) a radiation-emitting device associated with the cutting machine, (b) a plurality of receiving devices, one associated with each roof support, capable of receiving radiation emitted from the radiation-emitting device as the cutting machine passes in proximity to a receiving device and capable of generating a main electrical control signal in response to the receipt of such radiation, (c) a main control conductor connected to the receiving devices for carrying a main electrical control signal, (d) disabling means associated with each advance-initiating means and with the main control conductor for rendering an advance-initiating means non-responsive to a command signal applied to the advance-initiating means when the main electrical control signal is above a pre-determined value, and (e) attenuating means associated with the main control conductor between each pair of roof supports for attenuating the main electrical control signal to a value below the said pre-determined value when that signal has passed a pre-determined number of attenuating means from a receiving device receiving radiation from the radiation-emitting device.