Instruction manual

7
Line Code – Port 1 Only, Switch 4
Line code is the T1 mode of transmission. The two 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 – 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
TNE1500 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) alternates positive and
negative pulses.
Line Attenuation – Port 1 Only, Switches 5 and 6
Shorter distances between the TNE1500 and remote modems require increasing T1
transmit 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 transmit amplitude.
 0 dB – 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.
Table 5. Line Code Settings
Switch 4 Line Code
down Bipolar with 8 Zero Substitution
up Alternate Mark Inversion
Table 6. Line Attenuation Settings
Switch 5 Switch 6 Attenuation
down down 0 dB
up down –7.5 dB
down up –15 dB
up up –22.5 dB