User's Manual

ADCP-75-130 • Issue 3C • August 2006

Page 5

2.1.3 Fault Detection and Alarm Reporting

The DHU detects internal circuitry faults and optical port faults. Various front panel Light

Emitting Diode (LED) indicators turn from green to red or yellow if a fault is detected or an

optical input is lost. A set of alarm contacts (normally open and normally closed) are also

provided for reporting an alarm to an external alarm system when a fault is detected. Both

major alarm (all fault conditions except high temperature) and minor alarm (high temperature

fault condition) contacts are provided.

2.1.4 RF Signal Connections

The RF signal connections with the BTS are supported through two N-type female connectors.

One connector is used for coaxial cable connection of the forward path RF signal. The other

connector is used for coaxial cable connection of the reverse path RF signal. In most

installations, the DHU will not connect directly to the BTS but will be connected to an

interface device such as the RIU or the HPCP. Additional information concerning the DHU to

BTS interface is provided in the Digivance ICS Remote Interface Unit User Manual (ADCP-

75-178) and in the Digivance ICS 800 and 1900 MHz High Power Conditioning Panel User

Manual (ADCP-75-175).

Maximum output at the DRU antenna port is obtained when the level of the composite

forward path RF signal input to the DHU is 1 dB below the DHU overdrive level. The

maximum signal level the DHU will accept is determined by the DHU overdrive limiter. If the

input signal level is above a specified level, the overdrive limiter will incrementally insert

attenuation. The overdrive limiter protects the system against excessive inputs but does not

function during normal operation. The level of the RF signal output at the DRU is dependent

on the modulation protocol and the number of carriers.

2.1.5 Optical and Electrical Connections

The optical and electrical connections with the DRU’s and DEU’s are supported by six optical

and six electrical ports. Each optical and electrical port consists of a status LED, an RJ-45 DC

power jack, a port enabled/disable switch, and a small form factor LC-type optical transceiver

(available separately). Each transceiver is color-coded to identify whether it supports single-

mode (blue) or multi-mode (black/beige) fiber. An optical port may be connected to a DRU, a

DEU, or not used. An electrical port may be connected to a DRU or not used. Unused ports

are disabled via the corresponding port enable/disable switch. When disabled, the port LED is

off, the alarm reporting function is disabled, the laser is off, and the DC power is off. Enabling

the enable/disable switch activates all functions. The modular optical transceivers are

accessory items and are field replaceable.

2.1.6 Powering

The DHU is powered by 120–240 VAC (50/60 Hz) power which is supplied through a

standard three-conductor 120 VAC power cord. The power cord is provided with the DHU

and is 98 inches (2.5 meters) long. A resetable circuit breaker/On-Off switch is provided at the

unit front panel. The switch applies power to the DHU internal power supply.