In 1824, internal alterations were made to construct a new lighthouse tower through the original castle tower. This tower supported a new lantern and reflector array by
Robert Stevenson. In 1851 Robert's son,
Alan Stevenson, installed a first order dioptric lens at Kinnaird Head. The lens was standing and gave a fixed character. The site was further improved in 1853 with the site's first purpose-built accommodation blocks designed by brothers David and
Thomas Stevenson.
David Alan Stevenson further upgraded the site in 1902 by installing a flashing lens apparatus. The
hyperradiant Fresnel lens gave one flash every fifteen seconds and was visible for 25–27 miles. The lens was designed by David and his brother
Charles Alexander Stevenson, and was made by the
Chance Brothers. Only nine Scottish lights were given hyperradials,
Hyskeir and Kinnaird Head being the only stations to retain their hyperradials today. A foghorn was also built and was operational from 1903, giving a 7-second blast every 90 seconds. In 1906 the light was converted to incandescent operation. In 1929 Kinnaird Head became home to the first
radio beacon in Scotland. The fog signal was discontinued in 1987, although the horn is still in place. The original lighthouse is no longer operational and is now home to the
Museum of Scottish Lighthouses. A new automatic light was established beside the original light in 1991. == Anniversary events ==