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INTRODUCTION AND OPERATION
1.12.4 POWER SUPPLY
The 2000 Series Repeater Power Supply is a
quad output 800W supply with power factor correc-
tion. A battery back-up module, PN 023-2000-830,
can be added to the power supply to provide automatic
battery revert in the event of AC power failure (see
Section 2.4) The Battery Back-Up module charges the
batteries when AC is present at the power supply (see
Section 2.5 and 8.6).
1.13 REPEATER INFORMATION
1.13.1 INTRODUCTION
NOTE: The VIKING VX does not require a separate
LTR logic drawer.
The repeater model used in an LTR system is
determined by frequency range. 900 MHz systems
use VIKING VX (-232/234) or LTR 8900s, UHF use
1010s, and VHF use 1100s. Repeaters operate on a
single frequency (requires one repeater for each chan-
nel). The MPC in each repeater performs all control
and signaling functions on that channel. Information
is exchanged between repeaters via a high-speed data
bus (modular cable). No system controller is required.
Optional accessories, such as the Telephone
Interconnect Card (TIC) can be installed in the
repeater and the ID Validator drawer can be installed
in the repeater rack. Refer to Johnson LTR ID Valida-
tor Manual, Part No. 001-4408-501 and Johnson Tele-
phone Interconnect Card Manual, Part No. 004-2000-
370 for detailed information.
1.13.2 HOME REPEATERS
All mobiles have one of the site repeaters
assigned as its "Home" repeater. This is the repeater
from which it receives most of its control information.
When a mobile is not placing or receiving a call, it is
always monitoring its Home repeater to determine
which channel is free and if it is being called by
another mobile.
The Home repeater is always used to make a call
unless it is busy. When the Home repeater is busy,
any other repeater in the site may then be used. Up to
250 ID codes are assigned to each repeater. An ID
code and Home repeater number are the "address" of
October 1999
Part No. 001-2009-201
the mobiles in the system. Therefore, up to 1250 sep-
arate addresses can be assigned in a 5-repeater system
and up to 5000 can be assigned in a 20-repeater sys-
tem. An ID code may be assigned to an individual
mobile or a group of mobiles as required.
1.13.3 INTER-REPEATER DATA COMMUNICA-
TION
Data communication between VIKING VX and
LTR repeaters at a site is via a high-speed data bus.
This bus cable is installed in a daisy-chain manner
between repeaters. If both VIKING VX and LTR
repeaters are located at a site, 20 repeaters can be
interconnected. Refer to Section 2.9 for information
on connecting the data bus.
1.13.4 MOBILE TRANSCEIVERS
The mobile and handheld transceivers used in an
LTR system must be compatible with the type of sig-
naling in use and also the frequency range.
1.14 REPEATER DATA BUS SIGNALING
1.14.1 GENERAL
A single-line serial data bus interconnects the
logic units of all the LTR repeaters at the site. The
first repeater powered on generates the synchroniza-
tion pulse that is used by all other repeaters to deter-
mine their time slot on the data bus. If all repeaters are
powered on at the same time, the lowest numbered
repeater generates the synchronization pulse. There
are 21 slots with 1-20 used for repeater reporting and
21 used by the ID Validator (see Section 1.14.3). The
time slot used by a repeater is determined by the num-
ber assigned to that repeater by the programming in
the MPC. Repeater 1 uses time slot 1, repeater 5 uses
time slot 5, and so on. The data rate on the repeater
data bus is 18,750 bits per second.
In its time slot, each repeater places information
on the data bus indicating its status. If a repeater is
not busy, only start bits appear in its slot. If a repeater
is busy, it places in its slot the Home repeater and ID
code of the mobile receiving the call on that repeater.
If a repeater number is unassigned, nothing appears in
that time slot.
1-8
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