IMSA Traffic Signal Technician II Exam V1
1. In a NEMA TS2 Type 1 cabinet, what is the primary communication method between the
controller and the Bus Interface Units (BIUs)?
A. A-B-C connectors
B. RS-232 Serial Port
C. Synchronous Data Link Control (SDLC)
D. Ethernet Crossover Cable
Correct Answer: C
Rationale: NEMA TS2 Type 1 cabinets utilize the SDLC protocol to communicate between
the Controller Unit, BIUs, MMU, and other smart devices. This high-speed serial bus
reduces the amount of physical wiring required compared to TS1 standards. It operates at
153.6 Kbps and allows for standardized addressing of components.
2. Which component is responsible for monitoring the conflict of green, yellow, and walk
indications in a NEMA TS2 cabinet?
A. Auxiliary Switch Unit
B. Conflict Monitor Unit (CMU)
C. Bus Interface Unit (BIU)
D. Malfunction Management Unit (MMU)
,Correct Answer: D
Rationale: The Malfunction Management Unit (MMU) is the critical safety device in a
NEMA TS2 cabinet system. It monitors voltages on the field terminals to detect conflicting
greens or lack of proper clearance intervals. If a malfunction is detected, the MMU forces
the intersection into a flash condition to ensure public safety.
3. When troubleshooting an inductive loop that is ‘chattering,’ what is the most likely cause
related to the lead-in cable?
A. Proper grounding of the shield
B. High resistance in the loop turn
C. A poor splice or loose connection
D. Too many turns of wire
Correct Answer: C
Rationale: A chattering or intermittent loop detector signal is often the result of physical
degradation in the lead-in connection. Poor splices introduce variable resistance and noise
that the detector amplifier cannot filter effectively. Technicians should inspect splice kits
and terminal connections first when this symptom occurs.
4. What is the standard resistance value for a ground rod installation as recommended by
many traffic agencies to ensure transient protection?
A. 25 ohms or less
B. Exactly 50 ohms
, C. 100 ohms or more
D. 10 ohms exactly
Correct Answer: A
Rationale: According to the National Electrical Code and ITE standards, a ground
resistance of 25 ohms or less is preferred for electrical systems. Lower resistance facilitates
the rapid discharge of surge currents from lightning or power spikes. In many cases,
multiple ground rods must be bonded together to achieve this target value.
5. In traffic signal programming, what does ‘Minimum Green’ represent?
A. The time required for a pedestrian to cross the street
B. The time it takes for a vehicle to clear the intersection
C. The shortest duration a green indication can be displayed
D. The delay before a vehicle is detected
Correct Answer: C
Rationale: Minimum Green is the initial duration assigned to a phase to allow vehicles
waiting between the stop bar and the detector to start moving. It ensures that the signal
does not cycle so fast that a driver is caught by surprise or left stranded. This value is
determined based on the distance from the stop line to the first detector.
1. In a NEMA TS2 Type 1 cabinet, what is the primary communication method between the
controller and the Bus Interface Units (BIUs)?
A. A-B-C connectors
B. RS-232 Serial Port
C. Synchronous Data Link Control (SDLC)
D. Ethernet Crossover Cable
Correct Answer: C
Rationale: NEMA TS2 Type 1 cabinets utilize the SDLC protocol to communicate between
the Controller Unit, BIUs, MMU, and other smart devices. This high-speed serial bus
reduces the amount of physical wiring required compared to TS1 standards. It operates at
153.6 Kbps and allows for standardized addressing of components.
2. Which component is responsible for monitoring the conflict of green, yellow, and walk
indications in a NEMA TS2 cabinet?
A. Auxiliary Switch Unit
B. Conflict Monitor Unit (CMU)
C. Bus Interface Unit (BIU)
D. Malfunction Management Unit (MMU)
,Correct Answer: D
Rationale: The Malfunction Management Unit (MMU) is the critical safety device in a
NEMA TS2 cabinet system. It monitors voltages on the field terminals to detect conflicting
greens or lack of proper clearance intervals. If a malfunction is detected, the MMU forces
the intersection into a flash condition to ensure public safety.
3. When troubleshooting an inductive loop that is ‘chattering,’ what is the most likely cause
related to the lead-in cable?
A. Proper grounding of the shield
B. High resistance in the loop turn
C. A poor splice or loose connection
D. Too many turns of wire
Correct Answer: C
Rationale: A chattering or intermittent loop detector signal is often the result of physical
degradation in the lead-in connection. Poor splices introduce variable resistance and noise
that the detector amplifier cannot filter effectively. Technicians should inspect splice kits
and terminal connections first when this symptom occurs.
4. What is the standard resistance value for a ground rod installation as recommended by
many traffic agencies to ensure transient protection?
A. 25 ohms or less
B. Exactly 50 ohms
, C. 100 ohms or more
D. 10 ohms exactly
Correct Answer: A
Rationale: According to the National Electrical Code and ITE standards, a ground
resistance of 25 ohms or less is preferred for electrical systems. Lower resistance facilitates
the rapid discharge of surge currents from lightning or power spikes. In many cases,
multiple ground rods must be bonded together to achieve this target value.
5. In traffic signal programming, what does ‘Minimum Green’ represent?
A. The time required for a pedestrian to cross the street
B. The time it takes for a vehicle to clear the intersection
C. The shortest duration a green indication can be displayed
D. The delay before a vehicle is detected
Correct Answer: C
Rationale: Minimum Green is the initial duration assigned to a phase to allow vehicles
waiting between the stop bar and the detector to start moving. It ensures that the signal
does not cycle so fast that a driver is caught by surprise or left stranded. This value is
determined based on the distance from the stop line to the first detector.
