9600-Bit/Second Limited Distance VoiceBand Data Transmission Technique
Original Publication Date: 1979-Nov-01
Included in the Prior Art Database: 2005-Feb-20
This article describes a combination of: (1) a modulation technique, (2) a detection technique, and (3) a timing recovery technique all suitable for data transmission at 9600 bit/s over a voice-band channel with a passband of approximately 300 to 3600 Hz. The channel must not introduce frequency offset, as might be caused by an FDM (frequency division multiplexing) carrier system. (This condition is almost always true in the limited distance environment.) Equalization to counteract the effects of envelope delay and amplitude distortion will be necessary with this signaling scheme in many cases, e.g., when the local loop contains loading coils. The Subtractive Automatic Equalization technique described in the preceding article is compatible with the transmission method described herein.