Distance measuring equipment for sewer survey cameras - has microswitch operated by notches in hauling cable sheathing to check length of cable run

The distance measuring system comprises a vehicle-based winch and recording unit by which a surveying camera is drawn along the sewer duct. A light cord is first floated down stream between manholes. A hauling cable and power supply cable is then attached so that the inspection camera may be drawn through the section of sewer under investigation. The distance gauge comprises a pair of pivoted, horizontal arms, each with a free-running roller at one end. The upper of the two arms has a bracket which carries a screw-adjustable striker plate. The lower arm is fitted with a microswitch whose plunger is operated by the plate on the upper arm. The hauling cable attached to the camera at one end and the winch at the other, passes between the rollers. The cable has a plastics sheathing which has notches at 25 cm intervals.