1,207,968. Valves. ROTORK CONTROLS Ltd. 2 Nov., 1967 [15 Dec., 1966], No. 56164/66. Heading F2V. [Also in Division H1] In a limit switch arrangement for controlling the electric motor drive of a valve actuator shaft 44 and substantially the same as that of Specification 1,003,761, in which a guided nut 30 is movable between end stops 25, 40 on a threaded spindle 20, one end-stop comprises a pair of nuts 45, 46, Fig. 5, with an intermediate locking washer 47 which is prevented from rotating relatively to the shafts 20 as by a D- shaped hole engaging over a flat 48 on the shaft 20. Projections 51, 53, 54 on the end-stops and nut 30 are arranged to inter-engage at the limit positions to prevent binding between the relatively rotating members. The shaft 20 is hollow and rotatably mounted on an indicator shaft 28 geared at 15, 16 to the actuator output shaft 11. Friction clutch 24 with spring discs 25 is provided for driving the shaft 20 from indicator shaft 28, the pressure on the discs being adjustable by an external clamping nut 26. The arrangement whereby the nut 31 actuates notches 60-62 through striker plates 43, 65, 68 when it partially rotates or engaging an end stop is described in Specification 1,207,967. Lost-motion connections 71, 91 between the striker plates 43, 65, 68 and operation of the switches 60-62 through an overload shaft 75 and indicator shaft 44 are described in Specification 1,207,969. The use of the device with a fluid valve actuator as described in Specification 939,353 is referred to. Reference has been directed by the Comptroller to Specifications 1,003,761,1,003,764, 1,003,765, 1,003,766, 1,011,989 and 1,027,526.