CMU-24VDC-ITL Cabinet Monitor Unit
Operations Manual
Eberle Design Inc.
Page 1
Section 1
GENERAL
1.1 OVERVIEW
The model CMU-24VDC Cabinet Monitor Unit (CMU-24VDC) is the principle part of the ITS
Traffic Control Cabinet Monitoring System. It is resident in the Power Distribution Assembly
and communicates with an Auxiliary Monitor Unit (AMU) located in each Output Assembly
via Serial Bus #3. The role of the CMU-24VDC is to query various cabinet conditions and, if
the application requires action, the CMU-24VDC will transfer control from the Advanced
Traffic Controller (ATC) to a flashing control mode. Applications include the detection of,
and response to, improper and conflicting signals and improper operating voltages in a
cabinet assembly caused by malfunctions of the (ATC), load switches, or miss wiring of the
cabinet.
The communications between the ATC and the CMU-24VDC via Serial Bus #1 plays an
integral role in ensuring safe and proper operation of the cabinet equipment as well as
providing important diagnostic functions used for trouble shooting malfunctioning
equipment.
The Eberle Design CMU-24VDC meets with or exceeds all appropriate specifications
outlined the ASHTO/ITE/NEMA
Intelligent Transportation System (ITS) Standard
Specification for Roadside Cabinets
Version 01.02.17b
.
The Eberle Design CMU-24VDC is functionally interchangeable with a standard CMU-212
but is specially configured for low voltage (24Vdc) DC signal loads.
1.2 CHANNEL CONFIGURATION
The CMU-24VDC can be configured to monitor up to 28 physical load switch channels of
three inputs per channel. An additional four virtual channels can be programmed to provide
a total of 32 logical channels. Each channel is comprised of a Red / Don’t Walk input, a
Yellow input, and a Green / Walk input.
1.3 AUXILIARY MONITOR UNIT
The Auxiliary Monitor Unit (AMU-24VDC) provides the CMU-24VDC with voltage and
current measurements from each installed Output Assembly. The AMU-24VDC has the
capability to measure and report field terminal voltages for fourteen channels of three
inputs per channel and load currents for fourteen channels. The AMU-24VDC is also
compatible with a six position Output Assembly. The AMU is configured by its output
assembly address. This address is set by a jumper plug located on the rear of the output
assembly. For further information concerning the AMU-24VDC, see the Eberle Design
AMU-24VDC Operations Manual
.
The AMU-24VDC address assignment specifies the physical arrangement of the Output
Assemblies. This defines the number of contiguous channels that the CMU-24VDC is
monitoring. An AMU-24VDC assigned as a 14 channel unit must be addressed as AMU #1
with AMU #2 reserved, or as AMU #3 with AMU #4 reserved. The following table shows the
ten possible cabinet configurations:
AMU #1 AMU #2 AMU #3 AMU #4 Monitored Channels
14
reserved
none
None
1 thru 14
14
reserved
14
reserved
1 thru 28
14
reserved
6
None
1 thru 20
14
reserved
6
6
1 thru 26
6
none
none
None
1 thru 6
