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MMU2-1600GE series Operations Manual Rev Apr 2020 Page
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of 51
Section 2
General Characteristics
2.1
INPUTS
2.1.1
AC LINE
The over-current protected side of 120 volt AC 60 hertz source. This input (Connector A - Pin A) is used to
generate the voltages required to operate the monitoring logic. The monitor has a front panel mounted over-current
protection device in the 120 volt AC input to the unit. This fuse is a 1/4 AMP SLO-BLOW and should only be
replaced with a fuse of the same type and value.
Typical Connection: Cabinet AC Line power source.
2.1.2
AC NEUTRAL
The unfused and unswitched return side of the 120 volt AC 60 hertz power source. This input (Connector A - Pin
V) is the referenced signal for all field terminal voltage sensing inputs. This input is not connected to Logic
Ground or Earth Ground within the unit.
Typical Connection: Cabinet AC Neutral.
2.1.3
EARTH GROUND
The monitor has an input terminal (Connector A - Pin U) providing an independent connection to the chassis of the
unit. This input is not connected to Logic Ground or AC Neutral within the unit.
Typical Connection: Cabinet Earth Ground.
2.1.4
FIELD TERMINALS (REDS, YELLOWS, GREENS, AND WALKS)
The field terminal inputs are where the Red, Yellow, Green, and Walk indications are connected to the monitor.
The inputs used and how they are used is determined by the state of the Type Select input (See Section
2.1.11).
Type 16: Three inputs are provided for each channel to permit the monitoring of voltages at the Green, Yellow,
and Red signal field terminals. If the channel is used to monitor pedestrian indication, they are connected Don’t
Walk to Red, Pedestrian Clearance to Yellow, and Walk to Green.
Type 12: Four inputs are provided for each channel to permit the monitoring of voltages at the Green, Yellow,
Red, and Walk signal field terminals.
The thresholds used to determine the ON and OFF states of the field terminals can be modified from the standard
(incandescent) thresholds to ones more appropriate for LED field displays. The LED thresholds are more
restrictive than the standard thresholds. Therefore, you will not miss a fault using the LED thresholds that would
have been detected using the standard thresholds.
In the Standard Mode (Incandescent Field Displays):
A Green, Yellow, or Walk signal input is sensed as ON when it exceeds 25V
RMS
and a signal input is sensed
as OFF when it is less than 15V
RMS
. Signals between 15V
RMS
and 25V
RMS
may be in either state.
A Red signal input is sensed as ON when it exceeds 70V
RMS
and a signal input is sensed as OFF when it is
less than 50V
RMS
. Signals between 50V
RMS
and 70V
RMS
may be in either state.
In the LED mode (LED Field Displays):
For the purpose of testing for Conflicts, Multiple Indications, and Flashing Don’t Walk Monitoring, a Green,
Yellow, Red, or Walk signal input is sensed as ON when it exceeds 25V
RMS
and a signal input is sensed as
OFF when it is less than 15V
RMS
. Signals between 15V
RMS
and 25V
RMS
may be in either state.
For the purpose of testing for Red Fails, Co-Channel Childs, Short Yellows, and Short Clearance, a Green,
Yellow, Red, or Walk signal input is sensed as ON when it exceeds 70V
RMS
and a signal input is sensed as
OFF when it is less than 50V
RMS
. Signals between 50V
RMS
and 70V
RMS
may be in either state.
When the load connected to the sensing input of the monitor exhibits high impedance characteristics such as those
caused by some LED signal displays or burned out lamps, it may be necessary to place a low impedance device
(load resistor) external to the unit between the unit input and AC Neutral. See Section 6.2.4 of NEMA Standards
Publication TS 2-2003.
Typical Connections: Field terminals for channel Reds, Yellows, Greens, and Walks as appropriate.
2.1.5
RED ENABLE
The presence of the proper voltage at this terminal (Connector B - Pin a) enables the monitor to detect
the absence of voltage on all field signal inputs of a channel. The absence of the proper voltage inhibits
the detection of the absence of voltage on all field signal inputs of a channel. This input is considered
enabled when the input voltage exceeds 89V
RMS
at the Red Enable input. This function is considered
not enabled when the input voltage is less than 70V
RMS
at the Red Enable input.
