Abstract: A depth monitoring and valve lockout automatically resists operation of a valve when a wireline is being used within a well. The system utilizes components which can be attached to presently available wellheads, wireline lubricators, and accumulators without modification. A wellhead unit detects a beacon secured to a wireline lubricator to determine the wellhead for which the lubricator is being used. Proximity sensors detect proximity indicators secured to the wireline reel to detect rotation of the reel. Rotation of the reel is used to determine the presence of wireline within the wellhead having the wireline lubricator. An accumulator unit actuates linear actuators to move the presently existing lockout controls in response to the presence or removal of the wireline.