SSM-LE Series
Operations Manual
Eberle Design Inc.
Page 2
1.2.4 FLASHING YELLOW ARROW (FYA) PROTECTED-PERMISSIVE MOVEMENT
The SSM-LE Series is designed to monitor an intersection with up to four approaches using
the four section Flashing Yellow Arrow (FYA) movement outlined by the NCHRP Research
Project 3-54 on Protected/Permissive signal displays with Flashing Yellow Arrows. Two
cabinet configurations are supported depending on the number of load switches provided
and the capabilities of the Controller Unit. In both modes the SSM-LE Series has been
designed to provide the same broad fault coverage for the FYA approaches as it does for
conventional protected left turn phases including Conflict, Red Fail, Dual Indication, and
Minimum Yellow Clearance monitoring.
See section 3.11 for programming information.
1.3 GENERAL
The SSM-LE Series
is configured as a 6 channel (SSM-6LE) monitor or a 12 channel
(SSM-12LE) when operated in a TS-1 type cabinet assembly. Each channel has the
capability of monitoring a Green, a Yellow, a Red, and a Walk field signal output at the
Terminals and Facilities field terminals.
A Program Card is provided for assigning permissive channels. The SSM-LE Series
detects the presence of conflicting Green or Yellow or Walk field signal inputs between any
two or more channels not assigned to be permissive on the Program Card. The RED
ENABLE input, when activated, enables the Red Fail Monitoring functions of the unit
causing the monitor to trigger when it detects the absence of voltage on all three (four) of
the field signal inputs of a channel. It also enables the Minimum Yellow Clearance
Monitoring function which verifies that the Yellow Change Clearance interval between the
end of an active Green signal and the beginning of the Red signal is proper. The monitoring
circuitry is capable of detecting either full wave or positive and negative half-wave
sinusoidal field signal inputs at the specified voltage levels.
When triggered by the detection of a fault condition which exists longer than the minimum
period defined by the NEMA
Standards Publication TS1-1989 R2005
the SSM-LE Series
will enter the fault mode causing the OUTPUT relay to de-energize and two sets of contacts
on the OUTPUT relay to transfer. The cabinet assembly should be wired such that the
closure of the OUTPUT relay contacts will cause an automatic switching of the field signal
outputs from normal operation to flashing operation. The SSM-LE Series
will then display
the appropriate fault status. The loss of AC LINE will not reset the fault mode of the
OUTPUT relay contacts. In the event of AC LINE loss the SSM-LE Series
will retain the
status of all fault and channel indicators and will display the correct fault and channel status
upon restoration of AC LINE.
1.4 FIELD SIGNAL TERMINALS
A GREEN, YELLOW, or WALK field signal input will be sensed as active by the unit
when it
exceeds the Green, Yellow, or Walk Signal Detect voltage threshold (Section 7.1.2) and a
field signal input will be sensed as inactive when it is less than the Green, Yellow, or Walk
Signal No-Detect voltage threshold (Section 7.1.2). Both positive and negative half wave
rectified inputs will be sensed.
A RED (DON’T WALK) field signal input will be sensed as active by the unit when it
exceeds the Red Signal Detect voltage threshold (Section 7.1.2) and a field signal input will
be sensed as inactive when it is less than the Red Signal No-Detect voltage threshold
(Section 7.1.2). Both positive and negative half wave rectified inputs will be sensed.
NOTE: When the circuit connected to the sensing input of an MMU exhibits high
impedance characteristics such as caused by dimmers, burned out lamps, low wattage
equipment, or no load, it may be necessary to place a low impedance device external to the
unit between the MMU input and AC NEUTRAL (See Sections 5.5.3.9 and 6.2.4 of
NEMA
