he gained the title "Commissioner of Lighthouses." For 25 years, Putnam headed the bureau and during his administration, navigational aids saw a substantial increase. New technology was incorporated into the bureau's work, particularly in the area of electric aids and some automation using electricity. Though the number of aids to navigation increased substantially during Putnam's reign from 11,713 to 24,000, mostly buoys and small lights, arguably two of his most significant achievements were the passage of the Retirement Act for lighthouse personnel in 1918 and the introduction in 1921 of the radiobeacon as an aid to navigation. This new technology permitted a reduction of over 800 employees during Putnam's 25 years as head of the bureau. World War I During World War I and the period following, several technological advances contributed to the automation of lighthouses, rendering human occupancy unnecessary. A device for automatically replacing burned-out electric lamps in lighthouses was developed and placed in several light stations in 1916. A bell alarm warning keepers of fluctuations in the burning efficiency of oil-vapor lamps was developed in 1917. In the same year, the first experimental radiobeacon was installed in a lighthouse. The only lightvessel of the service sunk by enemy action was the LV-71 on August 6, 1918. After the sinking of the SS Merak by the near Diamond Shoals, North Carolina LV-71 rescued the survivors but was sunk as well shortly thereafter. Nobody was hurt in the action because the German commander allowed the Americans to evacuate the ship before firing. 1919–1939 The first automatic radiobeacon in the United States began service in 1928. Radiobeacons are still in use today, although most have recently been decommissioned as improved electronic navigational aids have become available. An automatic time clock for operating electric range lights came into use in 1926, and by 1933, a photo electric-controlled alarm device had been developed to check the operation of the unwatched electric light. A lightship staffed by remote control was equipped by the Lighthouse Bureau in 1934. It included a light, fog signal, and radiobeacon, all controlled by radio signals. A battery-powered buoy which gradually replaced the older acetylene buoys, was introduced in 1935. Because of the technological improvements mentioned above, and in particular the radio beacon direction finder, the United States rose from sixth in shipping safety in 1920 to second in 1935, with only the Netherlands holding a better safety record. Improvements