Frame Type, Line Code, Tx Transmit Buildout

NOTE Although all 24 channels continually run at 1,536 kbps, the Timeslot configuration for each port determines how many of the channels will be receiving data for that port. Ports configured to operate as fractional T1 lines require contiguous timeslots, as indicated in the table above.

Frame Type

Frame type is the T1 data encapsulation method. A frame consists of 193 bits (8-bit samples of each of the 24 T1 channels plus a synchronization bit) transmitted at a rate of 8,000 frames per second (1,544 kbps) across the T1 line.

Super Frame

Super Frame (SF) format assembles data into 12-frame transmission clusters.

Extended Super Frame (Default)

Extended Super Frame (ESF) format, used in Wide Area Networks (WANs), assembles data into 24-frame transmission clusters and integrates the following:

!Facilities Data Link (FDL) - communication support through in-service monitoring and diagnostics

!Cyclic Redundancy Check (CRC) - detects line errors and scrutinizes data integrity

Line Code

Line code is the T1 mode of transmission. The following line code options fall within the International Telecommunication Union - Telecommunication Standardization Sector (ITU-T) G.703 Standards for Transmission Facilities.

Bipolar with 8 Zero Substitution (Default)

Bipolar with 8 Zero Substitution (B8ZS) is used to accomodate the minimum ones density requirement in the North American public network. B8ZS line coding helps prevent loss of synchronization between the TAM1500-12 and remote T1 modems by using bipolar violations to guarantee there will always be pulses in the line.

Alternate Mark Inversion

The Alternate Mark Inversion (AMI) mode of transmission simply alternates positive and negative pulses. It is typical, with AMI, for a link to encounter long strings of zeros which can potentially cause loss of synchronization between remote units. Net to Net Technologies' products however, meet the North American minimum ones density requirement internally such that, even with AMI, loss of synchronization is prevented between the TAM1500-12 and remote T1 modems as it is with B8ZS line coding.

Tx (Transmit) Buildout

Shorter distances between the TAM1500-12 and remote modems require increasing line attenuation in order to prevent the T1 signal from becoming too strong for the repeaters, switches and other T1 transmission equiment that may be encountered along the line. Increased line attenuation translates into decreased transmit amplitude of the T1 signal.

210-0000025 rev04