US PATENT SUBCLASS 379 / 235
.~.~ Voice frequency signalling over trunk

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

219  DF  PLURAL EXCHANGE NETWORK OR INTERCONNECTION {6}
229  DF  .~ Interexchange signalling {6}
235.~.~ Voice frequency signalling over trunk

DEFINITION

Classification: 379/235

Voice frequency signalling over trunk:

(under subclass 229) Subject matter wherein control or supervisory signals are transmitted as tones within the audible frequency range.