“Thinking of ending it all? Call Bruce, PR1-0450, San Francisco Suicide Prevention.”

That was one of his first advertisements, posted on city buses. Bruce was a pseudonym. The phone rang once the first night. Half a century later, it rings nearly 200 times a day, and about 100 volunteers and 10 paid staff members are there to help.

Today, Suicide Prevention cites statistics showing that the city’s suicide rate is less than half what it was when the agency was founded. Hundreds of similar hotlines have since been set up in cities across the nation, and there is now a federally financed hotline, 1-800-273-8255, which receives tens of thousands of calls a month.

Mr. Mayes had no training in suicide counseling.

“I did feel that what was really needed was a compassionate ear, someone to talk to,” he told The San Francisco Chronicle in 2012. “It occurred to me that we had to have some kind of service which would offer unconditional listening, and that I would be this anonymous ear.”

While leading the prevention center, from 1961 to 1969, he continued to report for the BBC, filing feature stories from the West Coast. He also worked for local radio broadcasters, including KXKX, which was owned by the Presbyterian Church and later was bought by KQED, a public television station in San Francisco.

Mr. Mayes became the first general manager of KQED-FM, and in that role he was named a board member of National Public Radio, formed in 1970 by Congress and the Corporation for Public Broadcasting. He became its first chairman, and his signature is one of four on its articles of incorporation.