Hugh Downs, whose honeyed delivery and low-key but erudite manner helped make him a familiar face and voice on television for half a century, and whose career included long stints as host of both “Today” on NBC and “20/20” on ABC, died on Wednesday July 1 2020 at his home in Scottsdale, Ariz. He was 99. Mr. Downs’s 1986 memoir was called “On Camera: My 10,000 Hours on Television,” and that number was no idle boast: For years he held the Guinness-certified record for most total hours on commercial network television. (Regis Philbin eventually passed him.) Hugh Malcolm Downs was born in Akron, Ohio, on Feb. 14, 1921, the son of Milton and Edith (Hick) Downs. His father was a machinist and battery salesman, and the family moved to Lima, Ohio, when he was 2, and 10 years later to a farm outside Lima. Hugh accepted a scholarship to attend Bluffton College in Bluffton, Ohio. After a year, Hugh had to drop out to help support his family. He was hired as an announcer at WLOK, a radio station located not far from the farm. He moved to WWJ in Detroit in 1940 and, after serving briefly in the Army and receiving a medical discharge, joined the staff of WMAQ, the NBC station in Chicago. While in Chicago he met Dave Garroway. he came to New York in 1954 and was soon working as an announcer for Arlene Francis on “Home” and Sid Caesar on “Caesar’s Hour.” He joined “The Tonight Show” when Jack . Paar did, in 1957, and remained until Mr. Paar left in 1962. He was also host of the popular daytime game show “Concentration,” a job he held from 1958 until 1969. He also took Mr. Garroway’s old job as host of “Today.” He remained there for a decade. In June 1978, after seven years of freelancing, Mr. Downs received a call from Roone Arledge, the president of ABC News, asking him to take over the newsmagazine “20/20.” Mr. Downs was the sole host until 1984, when his former “Today” colleague Barbara Walters, who had been contributing to “20/20” for a few years, became his co-host. He remained with the program until retiring in 1999. Mr. Downs married Ruth Shaheen in 1944; she died in 2017. He is survived by their children, Hugh Raymond and Deirdre Lynn Downs; a brother, Wallace; two grandchildren; and four great-grandchildren.