| 摘要 |
A control means for use in a mining apparatus includes a radiation-emitting device on a cutting machine, a number of receiving devices, one associated with each roof support of the apparatus, for receiving radiation from the radiation-emitting device as the machine passes a receiving device, whereby a main control signal is generated, and advance-initiating means for each roof support, responsive to a command signal. A main conductor is connected to the receiving devices for carrying a main control signal, and disabling means is associated with each advance-initiating means and main conductor for rendering a said advance-initiating means non-responsive to a command signal applied to that means when the main control signal is above a pre-determined value. Attenuating means associated with the main conductor between each pair of roof supports is provided for gradually reducing the main control signal to a value below said pre-determined value. |
