IMSA Traffic Signal Technician II Exam V3
1. When troubleshooting a NEMA TS2 cabinet, what is the primary purpose of the Port 1 SDLC
(Synchronous Data Link Control) communication bus?
A. To provide 24VDC power to the cabinet components
B. To connect the cabinet to the central management system via fiber optics
C. To facilitate serial communication between the controller, MMU, and BIUs
D. To monitor the current draw of individual load switches
Correct Answer: C
Rationale: The Port 1 SDLC bus is a critical communication link in NEMA TS2 Type 1
cabinets. It allows the Controller Unit, Malfunction Management Unit (MMU), and Bus
Interface Units (BIUs) to exchange status and command data digitally. This reduces the
amount of physical wiring required compared to TS1 cabinets and enables advanced
diagnostic capabilities.
2. An inductive loop detector is showing a ‘Low Q’ or ‘Weak Signal’ error. Which of the
following is the most likely cause?
A. The loop sensitivity is set too high
B. Water penetration into the loop saw-cut or a nicked lead-in cable
C. The loop has too many turns of wire
,D. The lead-in cable is too short
Correct Answer: B
Rationale: A ‘Low Q’ error typically indicates that the loop circuit has a high resistance or
is leaking energy to the ground. This is most commonly caused by moisture entering the
loop wire insulation or the splice kit in the pull box. This degradation reduces the efficiency
of the inductive circuit and can lead to intermittent detections.
3. According to the MUTCD, what is the minimum duration for the yellow change interval at a
signalized intersection?
A. 1.0 seconds
B. 2.0 seconds
C. 5.0 seconds
D. 3.0 seconds
Correct Answer: D
Rationale: The MUTCD specifies that the yellow change interval should generally be
between 3 and 6 seconds. The specific duration is usually determined by engineering
judgment based on the approach speed and intersection geometry. Technicians must
ensure the controller timing matches the approved timing plan to avoid liability and safety
issues.
, 4. In a NEMA TS2 cabinet, which component is responsible for converting the serial data from
the controller into parallel outputs for the load switches?
A. The Power Supply
B. The MMU
C. The Flasher
D. The BIU (Bus Interface Unit)
Correct Answer: D
Rationale: The Bus Interface Unit (BIU) acts as the translator between the serial SDLC bus
and the physical cabinet hardware. It receives commands from the controller to turn on
specific phases and then activates the corresponding load switch outputs. BIUs are also
used to transmit detector inputs and cabinet status back to the controller.
5. When using an OTDR (Optical Time Domain Reflectometer) to test a fiber optic link, a sharp
downward vertical spike on the trace usually indicates:
A. A fusion splice
B. Normal attenuation over distance
C. Macro-bending in the fiber
D. A mechanical connector or a break
Correct Answer: D
1. When troubleshooting a NEMA TS2 cabinet, what is the primary purpose of the Port 1 SDLC
(Synchronous Data Link Control) communication bus?
A. To provide 24VDC power to the cabinet components
B. To connect the cabinet to the central management system via fiber optics
C. To facilitate serial communication between the controller, MMU, and BIUs
D. To monitor the current draw of individual load switches
Correct Answer: C
Rationale: The Port 1 SDLC bus is a critical communication link in NEMA TS2 Type 1
cabinets. It allows the Controller Unit, Malfunction Management Unit (MMU), and Bus
Interface Units (BIUs) to exchange status and command data digitally. This reduces the
amount of physical wiring required compared to TS1 cabinets and enables advanced
diagnostic capabilities.
2. An inductive loop detector is showing a ‘Low Q’ or ‘Weak Signal’ error. Which of the
following is the most likely cause?
A. The loop sensitivity is set too high
B. Water penetration into the loop saw-cut or a nicked lead-in cable
C. The loop has too many turns of wire
,D. The lead-in cable is too short
Correct Answer: B
Rationale: A ‘Low Q’ error typically indicates that the loop circuit has a high resistance or
is leaking energy to the ground. This is most commonly caused by moisture entering the
loop wire insulation or the splice kit in the pull box. This degradation reduces the efficiency
of the inductive circuit and can lead to intermittent detections.
3. According to the MUTCD, what is the minimum duration for the yellow change interval at a
signalized intersection?
A. 1.0 seconds
B. 2.0 seconds
C. 5.0 seconds
D. 3.0 seconds
Correct Answer: D
Rationale: The MUTCD specifies that the yellow change interval should generally be
between 3 and 6 seconds. The specific duration is usually determined by engineering
judgment based on the approach speed and intersection geometry. Technicians must
ensure the controller timing matches the approved timing plan to avoid liability and safety
issues.
, 4. In a NEMA TS2 cabinet, which component is responsible for converting the serial data from
the controller into parallel outputs for the load switches?
A. The Power Supply
B. The MMU
C. The Flasher
D. The BIU (Bus Interface Unit)
Correct Answer: D
Rationale: The Bus Interface Unit (BIU) acts as the translator between the serial SDLC bus
and the physical cabinet hardware. It receives commands from the controller to turn on
specific phases and then activates the corresponding load switch outputs. BIUs are also
used to transmit detector inputs and cabinet status back to the controller.
5. When using an OTDR (Optical Time Domain Reflectometer) to test a fiber optic link, a sharp
downward vertical spike on the trace usually indicates:
A. A fusion splice
B. Normal attenuation over distance
C. Macro-bending in the fiber
D. A mechanical connector or a break
Correct Answer: D
