IMSA Traffic Signal Technician II Exam V2
1. In a NEMA TS-2 Type 1 cabinet, which component is responsible for providing the primary
communication interface between the controller unit and the terminals and facilities?
A. A-B-C Connectors
B. RS-232 Serial Port
C. SDLC (Synchronous Data Link Control) Bus
D. Fibre Optic Transceiver
Correct Answer: C
Rationale: The SDLC bus is the core communication backbone of the NEMA TS-2 Type 1
architecture. It allows the controller, MMU, and BIUs to exchange data digitally without
massive wiring harnesses. This standardized protocol ensures that all frames are
synchronized and transmitted at high speeds for real-time operation.
2. When troubleshooting a ‘No Communication’ error between a central management system
and a field controller, what should be the first physical layer check?
A. Re-installing the controller firmware
B. Changing the IP address of the server
C. Checking the integrity of the transmission medium and connectors
D. Replacing the conflict monitor
,Correct Answer: C
Rationale: Physical layer issues such as loose connectors or broken cables are the most
common cause of communication failure. Technicians should always verify that the
hardware links are secure before moving to logical or software troubleshooting. This
approach follows the standard OSI model troubleshooting methodology.
3. Which of the following describes the ‘Dual Entry’ mode of operation in a signal controller?
A. A mode where both vehicles and pedestrians enter the intersection at once
B. Allows two controllers to operate one intersection
C. Permits two different timing plans to run simultaneously
D. Ensures that a non-conflicting phase is always timed with a called phase
Correct Answer: D
Rationale: Dual Entry is a programming feature used in multi-ring controllers to ensure a
phase is displayed in each ring. If a call is received for a phase in one ring and no call exists
in the other ring of the same concurrency group, the controller selects a pre-programmed
companion phase. This prevents a ‘dark’ approach on one side of the signal layout.
4. The Conflict Monitor (CMU) or Malfunction Management Unit (MMU) is designed to trigger
a flash state if it detects which of the following?
A. A light bulb burnout on a pedestrian signal
B. Conflicting green or yellow indications on different approaches
, C. A vehicle speeding through the intersection
D. Low battery on the controller’s internal clock
Correct Answer: B
Rationale: The primary safety function of the MMU/CMU is to prevent hazardous ‘Green-
Green’ conflicts. It monitors the voltage on the load switch outputs to ensure that
conflicting movements are never energized simultaneously. If such a condition occurs, the
unit drops the output to the flash transfer relays to secure the intersection.
5. What is the primary purpose of the ‘Yellow Change Interval’ in traffic signal timing?
A. To give pedestrians more time to finish crossing
B. To alert drivers that the green is about to begin
C. To allow for the discharge of the remaining queue
D. To warn drivers that the related green movement is being terminated
Correct Answer: D
Rationale: The Yellow Change Interval serves as a warning to approaching traffic that the
right-of-way is ending. It is calculated based on approach speed and deceleration rates to
allow a driver to stop or proceed safely. It is a critical safety component governed by
MUTCD standards.
1. In a NEMA TS-2 Type 1 cabinet, which component is responsible for providing the primary
communication interface between the controller unit and the terminals and facilities?
A. A-B-C Connectors
B. RS-232 Serial Port
C. SDLC (Synchronous Data Link Control) Bus
D. Fibre Optic Transceiver
Correct Answer: C
Rationale: The SDLC bus is the core communication backbone of the NEMA TS-2 Type 1
architecture. It allows the controller, MMU, and BIUs to exchange data digitally without
massive wiring harnesses. This standardized protocol ensures that all frames are
synchronized and transmitted at high speeds for real-time operation.
2. When troubleshooting a ‘No Communication’ error between a central management system
and a field controller, what should be the first physical layer check?
A. Re-installing the controller firmware
B. Changing the IP address of the server
C. Checking the integrity of the transmission medium and connectors
D. Replacing the conflict monitor
,Correct Answer: C
Rationale: Physical layer issues such as loose connectors or broken cables are the most
common cause of communication failure. Technicians should always verify that the
hardware links are secure before moving to logical or software troubleshooting. This
approach follows the standard OSI model troubleshooting methodology.
3. Which of the following describes the ‘Dual Entry’ mode of operation in a signal controller?
A. A mode where both vehicles and pedestrians enter the intersection at once
B. Allows two controllers to operate one intersection
C. Permits two different timing plans to run simultaneously
D. Ensures that a non-conflicting phase is always timed with a called phase
Correct Answer: D
Rationale: Dual Entry is a programming feature used in multi-ring controllers to ensure a
phase is displayed in each ring. If a call is received for a phase in one ring and no call exists
in the other ring of the same concurrency group, the controller selects a pre-programmed
companion phase. This prevents a ‘dark’ approach on one side of the signal layout.
4. The Conflict Monitor (CMU) or Malfunction Management Unit (MMU) is designed to trigger
a flash state if it detects which of the following?
A. A light bulb burnout on a pedestrian signal
B. Conflicting green or yellow indications on different approaches
, C. A vehicle speeding through the intersection
D. Low battery on the controller’s internal clock
Correct Answer: B
Rationale: The primary safety function of the MMU/CMU is to prevent hazardous ‘Green-
Green’ conflicts. It monitors the voltage on the load switch outputs to ensure that
conflicting movements are never energized simultaneously. If such a condition occurs, the
unit drops the output to the flash transfer relays to secure the intersection.
5. What is the primary purpose of the ‘Yellow Change Interval’ in traffic signal timing?
A. To give pedestrians more time to finish crossing
B. To alert drivers that the green is about to begin
C. To allow for the discharge of the remaining queue
D. To warn drivers that the related green movement is being terminated
Correct Answer: D
Rationale: The Yellow Change Interval serves as a warning to approaching traffic that the
right-of-way is ending. It is calculated based on approach speed and deceleration rates to
allow a driver to stop or proceed safely. It is a critical safety component governed by
MUTCD standards.
