| 摘要 |
<p>X.21 Switching System A system is disclosed to provide X.21 in-band call establishment signaling in the data path of a data communication system in a satellite communications controller. The system includes an X.21 signaling protocol between a data terminal equipment and the satellite communications controller on the terrestrial side and allows self-switched digital data port functions in lieu of associated voice port and line functions as practiced in the prior art. An important aspect is that the signaling rate is the same as the line data rate. At the start of the signaling state, the E input to the call processor is activated for the appropriate port. Call establishment signals are then processed through the digital switch and an X.21 adapter to the system's control processor. Finally the call establishment signaling has been completed and all data bits go through the digital switch and are transmitted to the digital interface. At the end of the call the data port goes back to the first, idle state. MA9-82-014</p> |
