While U.S. Robotics did not invent the modem, they
were one of the first
companies to sell them for home use. Here are some U.S. Robotics data sheets
that I got in February 1978.
http://www.swtpc.com/mholley/USR/USR_Modem.htm
I don't want to argue about who was first to sell a modem. I just think it
is neat that U.S. Robotics is still around and I have these data sheets
I've got a DC Hayes 300 baud S-100 modem. I think the date on it is 1977.
g.