Nortel DualMode 800, Maintenance Manual

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11-1
Wireless Solutions DualMode 800 Enclosure Maintenance Manual MTX08
DRU tests 11
Introduction
The DualMode Radio Unit (DRU) is a cell site transceiver and power
amplifier combination that operates in either a TDMA (digital) mode or in a
conventional AMPS (analog) mode. For a DualMode 800 Enclosure, the DRU
is packaged in two sub-modules, the Transmit Receive Unit (TRU) and the
Multi-Channel Power Amplifier (MCPA) module.
TRUs are datafilled as analog only, digital only, or dual-mode from the
Maintenance and Administration Position (MAP) terminal which is typically
located at the Digital Multiplex System-Mobile Telephone Exchange (DMS-
MTX). When datafilled as dual-mode, TRUs operate dynamically in either
AMPS or TDMA mode, based upon control from the switch. Whether
operating in AMPS or TDMA mode, the TRU uses the same internal DSP-
based circuitry to process both voice and data.
The use of Digital Signal Processing (DSP) technology greatly reduces
maintenance requirements. Due to functions being performed by software
code, rather than circuits composed of discrete elements that cause drift over
time and with temperature change, radio performance levels are improved and
routine maintenance schedules can be eliminated.
The DSP architecture of the TRU and microprocessor control of the MCPA
allow for very stable performance and consistency from one unit to another.
No manual adjustments are required on the TRU or the MCPA. There are, in
fact, no manual adjustable components in the TRU or MCPA. All adjustments
to operational parameters are made through the TRU terminal interface.
The most important item governing correct DRU operation is a proper, non-
corrupt, software load within the TRU. The TRU software load is
downloadable from the MAP position through a Peripheral Module (PM) load
tape. TRUs can be upgraded or reloaded with their operating software without
requiring anyone to visit a cell site.
Figure 11-1 and Figure 11-2 show the front panel layouts of the TRU2 and the
TRU3 respectively. Figure 11-3 shows the front panel layout of the MCPA.