CTC Union ETU01-Plus, User Manual

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Chapter 1. Introduction
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1.4 ETU01-Plus Capabilities
E1 link line coding
The ETU01-Plus and ETU01U-Plus support two E1 line codes:
AMI coding.
HDB3 coding.
E1 framing formats
The ETU01-Plus supports three formats:
Unframed format.
FAS (CCS, PCM-31) format.
MFAS (CAS, PCM-30) format.
The ETU01U-Plus supports only unframed format.
User data channel rates
The ETU01-Plus supports user data channel rates which are a multiple of 56 or
64kbps. For maximum flexibility, the ETU01-Plus supports data rates up to
2.048Mbps. The ETU01-Plus supports flexible time slot assignment, allowing the
user to freely specify the selection of time slots. The ETU01U-Plus supports
unframed operation with a data rate of 2.048Mbps only.
1.5 System Timing Considerations
The ETU01-Plus has the flexibility to meet the timing requirements of various
system configurations. The timing mode for the E1 link and the user data channel are
selected by the setting of DIP switches.
E1 link timing
The ETU01-Plus E1 link receive path always operates on the receive clock. The
ETU01-Plus recovers the receive clock from the received E1 link data signal. The
source of the ETU01-Plus E1 link transmit clock can be selected by the user.
The following E1 link transmit timing modes are available.
Recovery (loop back) timing:
The ETU01-Plus E1 link transmit clock is locked to the recovered receive clock.
This is usually the timing mode selected for network operation.
Internal timing:
The ETU01-Plus E1 link transmit clock is derived from the internal clock oscillator.
This timing mode is necessary in point-to-point applications over leased line. In this
case, one ETU01-Plus must use the internal oscillator, and the others must operate
from the recovered clock.
External timing:
The ETU01-Plus E1 link transmit clock is locked to the clock signal provided by the
user DCE connected to the data channel. When the data channel is used as the clock
source, the data channel must use clock timing mode 3 (DTE2) or 4 (DTE3).