| 摘要 |
The digital tie line provides a high speed pulse code modulation (PCM) digital path between private branch exchange (PBX) systems. The invention has a capability of providing a plurality of simultaneous two-way channels. By providing for twice the number of available channels in each PBX system, PBX systems may be interconnected by using one digital tie line per system, resulting in a non-blocking traffic situation between systems. High speed digital data may be directly passed via assigned channels between systems. The digital tie line provides a connection between the internal system parallel PCM bus and an externally located serial bus. A multiple PBX network can be interconnected by multiple external buses by employing a single digital tie line in each PBX system, per external bus. A modular time slot interchanger (MTSI) is used to direct signals between the system PCM bus and the external bus. The digital tie line may be employed for PCM voice and data processing, data switching, and other information communication applications. Connections to the external bus may be made via low cost coaxial cables. Manchester encoding of the serial external bus signal allows the external bus to retain timing and synchronization, and allows for shaping the power spectrum to permit relatively long cable lengths.
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