A 2500-Baud Time-Sequential Transmission System for Voice-Frequency Wire Line Transmission

The Sebit-25 is a full duplex terminal equipment designed to transmit digital data at rates up to 2500 baud. The equipment has been completely transistorized and thoroughly evaluated under environmental conditions. In operation, binary information at 2500 baud is converted to minimum bandwidth and used to amplitude modulate a 2500cycle carrier. The resulting signal is converted to vestigial sideband prior to transmission, to further compress the bandwidth. At the receiver terminal, amplitude and delay compensation are provided to correct for distortion introduced by the transmission line. Synchronous sampling of the recovered signal by a slaved time standard reproduces the original binary information even though line distortion may be severe. Excellent performance results were obtained from a series of laboratory tests conducted on the Sebit-25 to determine error probability vs noise, level changes, delay distortion, carrier frequency shift, and line filter variations.