| 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 | DF | .~.~.~ Modulated audio tone {4} |
| 93.31 | | .~.~.~.~ Protocol {3} |
| 93.32 | DF | .~.~.~.~.~> Initial setup |
| 93.33 | DF | .~.~.~.~.~> Having adjustable speed |
| 93.34 | DF | .~.~.~.~.~> Having recognition and selection |