MAS.632 Conversational Computer Systems - MIT OpenCourseWare

236 VOICE COMMUNICATIOK WITH COMPUTERS
cesses coordinated the setup and tear down of the call. For external calls, the
Etherphone provided ring detection for incoming calls and touchtone generation
to place a call, but switching occurred outside Etherphone in the ordinary telephone
network.
For basic telephony, Etherphone provided several methods of dialing a number
including a personal directory and dialing by name. A log was kept of all call
activity. Tools, primarily text-based (see Figure 11.2), provided user interfaces to
the dialing functions. For incoming calls, each Etherphone user had a distinctive
ring "tune" to distinguish whose phone was ringing when within earshot of
several offices. If the caller was also an Etherphone user, his or her ring tune
alternated with that of the called party, giving an audible form of calling party
identification. A telephone icon on the screen also indicated the incoming call and
visually displayed the caller's identity.
With local call routing and voice distribution over the Ethernet, a number of
new services were possible. The tight binding between a name and a telephone
number could be broken; while the called party was logged in on any workstation,
Etherphone calls could be forwarded to the nearest Etherphone. While in another
office, an Etherphone user could enable "call visiting" from any workstation,
causing one's calls to forward to that office. Because incoming calls were indicated
with the distinctive ring tune, the host and visitor knew who should answer the
telephone. A meeting service allowed multiple listeners to tune in to a meeting
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Figure 11.2. Etherphone telephone tools. (From Zellweger, Terry and
Swinehart, "An Overview of the Etherphone System and its Applications."
Reprinted with permission from Proceedingsof 2nd IEEE Conference on
Computer Workstations ©1988,IEEE.)
Courtesy of IEEE. Used with permission.