MIM2-A2-GZ41-00
October 2004
7
Line Code
Line code is the T1 mode of transmission. The two line code options outlined
below both 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 accommodate the minimum ones density requirement in the
North American public network. B8ZS line encoding helps prevent loss of
synchronization between the MIM-2T1 and remote T1 equipment by using
bipolar violations to guarantee the presence of pulses in the T1 line.
Alternate Mark Inversion – Alternate Mark Inversion (AMI) simply alternates
positive and negative pulses. Although AMI links typically encounter long
strings of zeros which can potentially cause loss of synchronization between
units, Paradyne products meet the North American minimum ones density
requirement internally such that loss of synchronization is prevented between
the MIM-2T1 and remote T1 equipment with AMI just as it is with B8ZS.
Line Attenuation
Shorter distances between the MIM-2T1 and remote modems can require an
increase in T1 line attenuation in order to prevent the T1 signal from becoming too
strong for repeaters, switches, and other T1 transmission equipment that may be
encountered along the line. Increased line attenuation translates to decreased T1
transmission amplitude.
0 dB (Default) – Receivers on most newer T1 transmission equipment can
automatically adjust for incoming amplitude, allowing them to run at zero
attenuation regardless of distance.
–7.5 dB, –15 dB, –22.5 dB – Some older T1 transmission equipment cannot
automatically adjust for incoming amplitude and line attenuation must be set
accordingly.
