Handbook

Axell Wireless Limited
Technical Literature
WMATA CRCS Redundant Antenna System
General Overview
Document Number 60-228701HBK Issue No. 3 Date 28/05/2010 Page 80 of 114
The Automatic changeover of the transfer relay function can be overridden by selecting the Manual position
of the switch labeled “AUTO / MANUAL” (annotated “S” in section 5.12.5.), the GREEN LED labeled “AUTO”
(annotated “DD in section 5.12.5.) is illuminated when in the Auto mode, the YELLOW LED labeled
“MANUAL” (annotated “EE” in section 5.12.5.) will illuminate when the Manual mode is selected. In the
Manual mode, the switch labeled “RX 1 / RX 2” (annotated “T” in section 5.12.5.) enables the signal source
to be manually selected between Primary and Redundant paths.
When the Transfer Relay has selected the Redundant path, the RED LED labeled “RELAY” (annotated “AA”
in section 5.12.5.) will illuminate.
In the reverse direction back to the Donor base station, the Uplink signals from the external Combiner Unit
60-228907 enters the RF Failover Switch Unit via the N type port labeled “REMOTE U/L” (annotated Kin
section 5.12.5.) and passes through a 30dB Directional Coupler 90-852330 which couples off the signal to
provide a monitor/test port labeled “UL MON -30dB” (annotated “L” in section 5.12.5.) for the Uplink input.
The Uplink path then passes through the Uplink RF Transfer Relay 96-900045 which is normally set to pass
the Uplink signal along the Primary Uplink path to the Jackson Graham Building CRAS System by way of
Dual Fiber Optic Unit 60-228703; this path exits the RF Failover Switch Unit via the N type port labeled
“PATH 1 U/L” (annotated “M” in section 5.12.5.) but if the RF Transfer Relays 96-900045 have been
switched from the Primary to the Redundant paths then the Uplink signal is diverted to the Redundant path
to the Carmen Turner Facility CRAS System by way of Dual Fiber Optic Unit 60-228703, this path exits the
RF Failover Switch Unit via the N type port labeled “PATH 2 U/L” (annotated “N” in section 5.12.5.)
RF Failover Switch Unit 60-228905 is powered by a 24V DC supply from one of the PSU Modules 96-
300091 in PSU Housing Shelf 96-300090, The 24V DC supply powers two on-board DC/DC converters 96-
200024 arranged in a parallel dual redundant configuration, the outputs of which are combined by power
diodes to provide a 12V DC supply active modules within the unit
Each of the two LPAs and the dual DC/DC convertors are monitored for alarms, should a fault occur the
front panel RED LED labeled “ALARM” (annotated “R” in section 5.12.5.) will illuminate and a contact alarm
relay output will be activated on “D” panel plug labeled “ALARM” (annotated “EE” in section 5.12.5.) the
status of the Transfer relay is also indicated on the Alarm connector.
5.12.1. RF Failover Switch Unit 60-228905 List of Major Sub-Components
Component
Part
Part Description Qty Per
Assembly
12-030301 1W Low Power Amplifier 2
17-019805 RF Detector Module 2
20-001601 12V Dual Relay Board 3
90-852320 20dB Directional Coupler 2
90-852330 30dB Directional Coupler 2
93-000065 8dB In-line Attenuator 2
93-930007 1W Load Termination 2
94-100003 Power Diode 2
96-110013 3.15A Fuse 1
96-200024 DC/DC Converter 2
96-900045 RF Transfer Relay 2
96-920002 DPDT Mini Toggle Switch 2