
XRT7300
E3/DS3/STS-1 LINE INTERFACE UNIT
REV. 1.1.2
27
that the transmitted data and clock can be recovered
reliably.
The Use of the Receive Equalizer in a Typical DS3
or STS-1 Application
Most System Manufacturers of equipment supporting
DS3 and STS-1 lines interface their equipment to a
Digital Cross-Connect System. While installing their
equipment, the Transmit Line Build-Out circuit is set
to the proper setting that makes the transmit output
pulse compliant with the Isolated DSX-3 or STSX-1
Pulse Template requirements. For the XRT7300 this
is achieved by setting the TXLEV input pin or bit-field
to the appropriate level.
When the System Manufacturer is interfacing the Re-
ceive Section of the XRT7300 to the Digital Cross-
Connect system, they should keep aware of the fol-
lowing facts:
1. By definition, all DS3 or STS-1 line signals that
are present at the Digital Cross-Connect system
are required to meet the Isolated Pulse Template
Requirements per Bellcore GR-499-CORE for
DS3 applications or Bellcore GR-253-CORE for
STS-1 applications.
2. Further, these Bellcore documents state that the
amplitude of these pulses at the DSX-3 or STSX-
1 can range in amplitude from 360mVpk to
850mVpk.
3. Finally, these Bellcore documents stipulate that
the Receiving Terminal must be able to receive
this pulse-template compliant line signal over a
cable length of 0 to 450 feet from the Digital
Cross Connect system.
Design Considerations for DS3 and STS-1 Appli-
cations
When installing equipment into environments as de-
picted in Figure 15, it is recommended that the Re-
ceive Equalizer be enabled by setting the REQDIS in-
put pin or bit-field to "0". In fact, the only time that the
Receive Equalizer should be disabled is when there
is an off-chip equalizer in the Receive path between
the Digital Cross-Connect system and the RTIP/
RRING input pins or, in applications where the Re-
ceiver is monitoring the transmit output signal directly.
FIGURE 18. THE TYPICAL APPLICATION FOR THE SYSTEM INSTALLER
DSX-3
or
STSX-1
Digital Cross-
Connect System
Transmitting
Terminal
Receiving
Terminal
0 to 450 feet of
Cable
Pulses that are
compliant to the
Isolated DSX-3 or
STSX-1 Pulse
Template
Requirement
0 to 450 feet of
Cable