 For many years, the Bell System (AT&T) maintained a monopoly on the use of its phone lines and what devices could be connected to them.However, in the Federal Communications Commission's (FCC) seminal "Carterfone Decision" of 1968, the FCC concluded that electronic devices could be connected to the telephone system as long as they used an acoustic coupler.Since most handsets were supplied by Western Electric and thus of a standard design, acoustic couplers were relatively easy to build.