210-0000036 rev03
Frame Type
Frame type is the E1 data encapsulation method. A frame consists of 248 bits (8-bit samples of
each of the 31 E1 channels plus a synchronization bit) transmitted at a rate of 8,000 frames per
second (1,984 kbps) across the E1 line.
Cyclic Redundancy Check (Default)
The Cyclic Redundancy Check (CRC) detects line errors and scrutinizes data integrity
across the E1 line by appending a CRC character to the end of the data block. The
character is a hexadecimal value calculated from the contents of each data block. The
remote modem makes a similar calculation upon receipt of each data block and requests
retransmission if there is a difference. CRC may be disabled on the EAM200-12 through
Net to Net's Network Management System (NMS). For further instruction, refer to the
Management User Guide for IP and Mini DSLAMs.
Line Code
Line code is the E1 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.
High Density Binary 3 (Default)
High Density Binary 3 (HDB3) is used to accommodate the minimum ones density
requirement in the European public network. HDB3 line coding helps prevent loss of
synchronization between the EAM2000-12 and remote E1 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 European minimum ones density requirement
internally such that, even with AMI, loss of synchronization is prevented between the
EAM2000-12 and remote E1 modems as it is with HDB3 line coding.
Timing
Local (Default)
The transmit clock source will originate from an oscillator onboard the EAM2000-12.
Loop
The transmit clock source will originate from the remote E1 modem.
NOTE
Although all 31 channels continually run at 1,984 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 E1
lines require contiguous timeslots, as indicated in the table above.
