actuated either to extend or retract by the switching valve 60 and its swing lever 65 the hose 31 is provided at its two ends with couplings 80 and 81 of the plug and socket type the hose 31 is connected with the corresponding distributor plate 16 by means of the coupling 80 and with the actuator 32 39 by means of the coupling 81 the hose 31 has such a length that the actuator 32 39 may be mounted either on the righthand or the lefthand adjacent roof support unit so that proximity control can be effected from either side the roof support control system described above may be easily adapted for two way proximity control without need to modify the valve assemblies 13 in this case instead of hoses 31 and actuators 32 39 special actuators 80 39 see fig2 are used each actuator 80 39 consists of a plurality of rotary slide valves operated by a hand lever 81 39 each actuator 80 39 may be connected to its control valve assembly 13 either directly or by extension hoses moreover the actuators 80 39 of adjacent roof support units are interconnected by multicore hydraulic hoses 82 each actuator 80 39 has sixteen switching positions twelve positions serving for actuating six functions namely six switching positions for actuating six functions on the adjacent lefthand roof support unit and six positions for actuating six functions on the adjacent righthand roof support unit the remaining four switching positions.