Section 311-580-20B
030-101527 Rev. B
3
0407IBRB
2.1
Transmission Design
2.1.1
T1 Span - Copper Applications
2.1.1.1
Normal T1 span design allows from 0 to 15dB of loss
from the last repeater in the span to the customer interface and
a maximum loss of 7.5dB for inside wiring to the CPE (see
Figure 2). This represents a total loss of 22.5dB. This mode pro-
vides a receive transmission path that can be configured to pass
the signal from the span to the CPE with either no net regenera-
tion or with the optional regenerator to 0dB DSX. The optional
regenerator in this path can be used in applications where the
maximum loss of 22.5dB to the CPE cannot be achieved other-
wise, or in special situations where the customer requires a 0dB
DSX handoff.
2.1.1.2
The unit’s transmit path from the CPE to the Network
provides a selectable 0 to 22.5 dB LBO as well as an automatic,
self-aligning LBO (Line Build Out) circuit to meet route junc-
tion and end section design requirements in T1 span
applications.
2.1.2
T1 Fiber Applications
When T1 service to a customer is provided via fiber, the unit can
be configured to serve as a maintenance interface between the
fiber mux and the CPE. The unit can be located up to 220 feet
from the mux. See Figure 3. In this mode, the unit can be provi-
sioned for CPE-to-FAC regeneration which will regenerate
CPE input levels that have been attenuated from 0 to 30dB to a
normal 0dB DSX. This is useful due to the fact that the DS1 low-
speed tributary ports of most multiplexers are designed to
accommodate input levels that have been attenuated no more
than 3dB from 0dB DSX. This feature allows for greater section
losses to be accommodated. The CPE-to-FAC regeneration fea-
ture allows the unit to be used in applications that previously
required a T1 Extension Repeater.
2.2
Power
2.2.1
Local Power
The NIU can be powered either from the T1 span or from a local
external supply. When locally powered, the supply should be 22
to 56Vdc and can be either a positive or negative ground refer-
ence. This allows the NIU to operate from +24Vdc supplies at
certain wireless and PCS (Personal Communication Service)
sites. In the local power mode, the NIU completes the T1 span
simplex power loop and drops negligible span voltage.
2.2.2
Span Power - Loop Mode
When optioned for Span Power - Loop Mode, the unit is pow-
ered remotely from the last serving office via the transmission
simplex leads. The unit will operate with a simplex current rang-
ing from 57 to 63 mA and will drop 24 Volts nominal at 60mA.
In addition, in the Span Power - Loop Mode, the unit will serve
as a termination device for span power by looping the simplex
current back on the FAC OUT simplex lead.
3.
TRANSMISSION FEATURES & OPTIONS
The NIU can be configured to operate in multiple applications.
The specific transmission provisioning is dependent on the ap-
plication. To facilitate this discussion, refer to Figure 4 for a
simplified diagram of the NIU transmission path during normal
operation.
3.1
RCV Path: Facility to CPE (A to Z Direction)
3.1.1
The incoming DS1 bit stream from the facility enters
the NIU on the FAC IN port and is transformer coupled into the
receive path circuitry. To facilitate circuit testing, a front-panel
bantam jack (FAC MON) provides monitor access to the receive
path.
3.1.2
The FAC-to-CPE path is continuously monitored for
loss of signal, control codes and performance statistics by vari-
ous detectors that operate over an input signal range of 0 to
-30dB DSX, and are unaffected by cable length or terminations
on any port or signal state of the CPE. If the FAC IN signal level
goes below -30dBDSX for more than 150ms, a FAC-to-CPE
path Loss-Of-Signal condition is declared, the front-panel
FLOS LED lights solid red and an Alarm Indication Signal
(AIS) is sent to the CPE.
3.1.3
FAC-to-CPE Regen
With FAC-to-CPE Regen enabled, the NIU will regenerate in-
put levels that have been attenuated from 0 to 30dB to a nominal
0dB DSX to the customer interface. The FAC-to-CPE Regen is
a selectable option that can be set remotely via TL1 or 16-bit
commands or locally via the craft terminal interface port. With
Figure 2.
Metallic T1 Span Applications
CPE
15dB
7.5dB
22.5dB
Network
Interface
NIU
LINE
RPTR
Figure 3.
Lightwave/Mux Fiber Applications
CPE
15dB
7.5dB
22.5dB
Network
Interface
M
U
X
NIU
LBO
220 feet
