CSI CSI-DSP85-250-AW Product Manual Download Page 13

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Circuit Operational Description

The repeater uses a single down-conversion/up-conversion scheme. There are multiple RF amplifier stages
prior to each down-converting mixer. The down-converting mixers are followed by a single IF amplifier. A Digital
Signal Processor block then processes the resultant digitized IF signal that was previously generated by an
Analog-to-Digital Converter. The processed (filtered) digital signal is fed to a Digital-to-Analog converter and then
up-converted to RF. A driver amplifier and a final power amplifier make up the final gain stages before application
to the diplexer. The maximum total system gain (diplexer input to diplexer output) is nominally 85 dB for either the
downlink or the uplink paths with both links having independent manual and automatic gain controls (AGC).

AGC reacts to analog power detection on both the input and output of the uplink and downlink RF chains.
A control algorithm continuously monitors these detected values and dynamically adjusts various gain
stages such that the net system gain value, entered manually, is optimally maintained without either
exceeding FCC parameters or overdriving the A/D converters.

An LED on the front panel provides immediate visual indications of the unit’s primary power and major or
minor alarm status. The repeater features automatic shutdown protection, as a safety measure, should
excessive drive be applied to the input or an oscillation condition occur. When in a protected mode, a
control algorithm determines the appropriate method of recovery to a normal, previously defined state, or
maintains the protection until manually reset. If recovery has been established, the LED will either be
extinguished or available to be reset. The events that trigger the error will be saved in the event log.

Important Installation Notes

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Inadequate isolation between the outside and inside antennas may cause regenerative

feedback in the system. This feedback can cause the amplifier to emit a continuous signal at
maximum amplitude and, in some cases, interfere with normal operation of the cell site. Careful
consideration of the layout and placement of the system is imperative.

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The installer should refer to the Safety Guidelines section on page 4 and the Important Safety

Information section on page 5 for proper antenna selection and installation. To avoid serious injury or
death and damage to the repeater, do not install donor or server antennas near overhead power lines
or high power components. Allow enough distance so that if antennas should fall they will not come
in contact with those components.

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Close proximity to the donor or server antennas with the repeater in operation may expose

the user or installer to RF fields that exceed FCC limits for human exposure.

WARNING!

AMPLIFIER OR HANDSET DAMAGE

MAY

OCCUR IF A HANDSET IS CONNECTED DIRECTLY

TO THE REPEATER OR THE COAX THAT LEADS TO THE REPEATER.

Optional Accessories

A complete line of accessories is available from Cellular Specialties, Inc. Check with your CSI distributor for

any additional items needed. Below are just a few examples suitable for most in-building needs.

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