Digital Host Unit Description - ADC Digivance Installation And Operation Manual

1.1.4 Digital Fiber Optic Transport
The DHU is connected to each DRU unit over a pair of multi-mode fiber optic links. One link
is used to transport the forward path optical signal. The other link is used to transport the
reverse path optical signal. Because the optical signal is digital, no adjustments to the optical
signal level are required at the DRU or the DHU regardless of the length of the optical link.
Either 50 or 62.5 micron core multi-mode fiber optic cable may be used for the optical link. If
50 micron cable is used, the optical link may be up to 750 meters in length. If 62.5 micron
core cable is used, the optical link may be up to 500 meters in length. The fiber optic links are
terminated with LC connectors.
1.1.5 Capacity for Expansion and Extended Runs
The DEU enables 6-way expansion of any optical port. This makes it possible to add more
DRUs without having to install additional DHUs. Each DHU is equipped with six optical
ports. If more than six DRUs are required by the application, a DEU may be connected to one
of the optical ports at the DHU which expands that port to six ports. If still more optical ports
are required, then a second DEU may be connected to the DHU or a second DEU may be
connected to the first DEU. The ability to cascade DEU's in parallel or in series provides
unlimited flexibility. It is physically possible to connect an unlimited number DRUs to the
DHU through the installation of DEUs. The maximum number of DRUs that can connected to
the DHU is limited only by the cumulative noise effect caused by antenna combining.
1.1.6 Power Requirements
The DHU, DEU, LIU, and RIU are each powered by 120–240 Vac (50–60 Hz) power which is
supplied through a standard three-conductor AC power cord. The DRU is powered by 34–48
Vdc which is supplied by either the DHU, DEU, or an ac/dc wall-mount style converter. When
the DRU is powered by the DHU or DEU, the power is fed through a category 3 or 5 cable
terminated with male RJ-45 connectors.
1.1.7 Fault Detection and Alarm Reporting
LED indicators are provided on the front panel of the various units to indicate if the system is
normal or if a fault is detected. In addition, normally open and normally closed alarm contacts
(for both major and minor alarms) are provided at the DHU for connection to a customer
provided external alarm system. This could be a local system or automatic call-out system.

1.2 Digital Host Unit Description

The DHU, shown in Figure 2, serves as the BTS servicing unit for the Digivance ICS. The
DHU provides the following basic functions:
•
RF inputs and outputs
•
Optical interface to the DRUs or DEUs
•
Digitizing of the cellular forward path RF signal
ADCP-75-110 • Issue 2B • July 2001
© 2001, ADC Telecommunications, Inc.
Page 3