| 摘要 |
A dual mode phone line connectivity mechanism allows POTS access and digital transport access to coexist over the same local loop serving a customer site, while providing a net DS0 data rate for customer data communications (e.g., either 56 kbps or 64 kbps). When the customer's analog device is on-hook, the connectivity mechanism is configured to provide a digital path for the local loop, so that a digital link, exclusive of voice-processing, is established between a terminal adapter (or super-modem) and the service provider's line interface card, which replaces the voice path with a digital transceiver for the duration of the call. Local loop-associated and network-associated switches selectively provide one of two alternative signalling paths-a voice signalling path containing a codec for POTS signalling, and a data signalling path. A loop current detector monitors the local loop, while a network monitor circuit monitors the network for a ring command signal. Outputs of these monitor circuits are coupled to switch control logic, which also looks for digital equipment wake-up tones and synchronization signals associated with digital access for terminal equipment.
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