On April 3, 1973, Cooper and Mitchell demonstrated two working phones to the media and to passers-by prior to walking into a scheduled press conference at the New York City Hilton in midtown Manhattan. Standing on Sixth avenue near the Hilton, Cooper made the first handheld cellular phone call in public from the prototype DynaTAC. The call connected him to a base station Motorola had installed on the roof of the Burlington House (now the AllianceBernstein Building) and into the AT&T land-line telephone system. Reporters and onlookers watched as Cooper dialed the number of his chief competitor Dr. Joel S. Engel at AT&T. "Joel, this is Marty. I'm calling you from a cell phone, a real handheld portable cell phone." That public demonstration landed the DynaTAC on the July 1973 cover of "Popular Science" Magazine. As Cooper recalls from the experience: "I made numerous calls, including one where I crossed the street while talking to a New York radio reporter – probably one of the most dangerous things I have ever done in my life."