US PATENT SUBCLASS 379 / 93.28
.~.~.~ Modulated audio tone

Current as of: June, 1999
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379 /   HD   TELEPHONIC COMMUNICATIONS

90.01  DF  TELEPHONE LINE OR SYSTEM COMBINED WITH DIVERSE ELECTRICAL SYSTEM OR SIGNALLING (E.G., COMPOSITE) {8}
93.01  DF  .~ Having transmission of a digital message signal over a telephone line {9}
93.26  DF  .~.~ By voice frequency signal (e.g., tone code) {3}
93.28.~.~.~ Modulated audio tone {4}
93.29  DF  .~.~.~.~> Reconfigurable
93.31  DF  .~.~.~.~> Protocol {3}
93.35  DF  .~.~.~.~> Having call-waiting
93.36  DF  .~.~.~.~> Line powered

DEFINITION

Classification: 379/93.28

Modulated audio tone:

(under subclass 93.26) Subject matter wherein a pulse or data signal causes a variation in the frequency, phase, or amplitude of an audible tone.

SEE OR SEARCH CLASS

375, Pulse or Digital Communications,

222, for modems.