an extra DA/AD conversion, which prohibits a V.90/92 connection, and also adds at least 3 dB of quantization noise and a small amount of bandwidth restriction, all of which combine to usually disallow 28.8K connections. Note that for modems which can measure Signal-to-Noise Ratios, 37 dB is the *best* that can be obtained on a connection through any form of 64Kbps/channel PCM digital carrier. The specification for a voice grade telephone dial up services, , ND up services dial up services, dial North Dakota, dial up services
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