Qwest DS-3 service provides high speed digital transmission capability between customer locations. It is delivered on fiber optic technology that transmits information in the form of light pulses through strands of glass. DS-3 service offers a high capacity channel that transmits 44.736 Mbps of isochronous serial data using a line code of Bipolar Three Zero Substitution (B3ZS) with transmission availability of 99.93 percent.

Binary 3 Zero Substitution (B3ZS)

B3ZS is an error checking process to ensure that the DS-3 44.7 Mbps clear channel has verified that the data transmitted in the signal is accurate. The method used by the equipment to transmit DS-3 operates within industry standards using B3ZS line code by modifying an Alternate Mark Inversion (AMI) line code algorithm. It replaces all occurrences of three consecutive binary zeros with a standard code word containing a higher one's density. Receiving equipment replaces that code word with three zeros as originally intended. With this industry standard line code, there are no constraints on the quantity of zeros in the customer-transmitted data.

DS-3 is a highly secure service that offers end-to-end digital transmission with a bandwidth totally dedicated to specific customer applications. It is used where availability and reliability requirements are key for mission-critical applications. This service can be channelized or multiplexed to provide up to 28 DS-1 circuits (equivalent to 672 DS0 channels). Multiplexing voice and lower speed digital channels as well as exchange services offers economies of scale and more control over network management.

DS-3 service is available in the contiguous United States and, on an intraLATA basis only, in the states of AZ, CO, IA, ID, MN, MT, NE, NM, ND, OR, SD, UT, WA and WY.

DS-3 Network Channel Interface (NCI) code options are:

• M-Framed, unchannelized, may be C-Bit Parity
• M23 multiplexing allows for channelization of the DS-3 with 28 DS-1s
• M23 multiplex with C-Bit Parity (limited availability)

DS-1 to DS-3 multiplexing schemes for either DS-1 line code formats of Alternate Mark Inversion (AMI) or Binary 8 Zero Substitution (B8ZS) are available formats for the aggregation of DS-1 traffic. Back to DS3