Some of the things the "121" law mandated were:

1. Actuation and release times

2. Mechanically applied spring brakes

3. Service air tank requirements

4. None of the above

5. All of the above

In order to understand a trailer brake system we must be able to answer, "how the system is charged" and "how the parking and emergency brakes work" and:

1. How the service brake systems works

2. How much air the compressor pumps

3. How many feet it takes to stop the rig

4. A & C

5. None of the above

Which valve takes air from the trailer air tanks and sends it to the service brake chambers to apply or release the service brakes?

1. Two-way check valve

2. One-way check valve

3. Service relay valve

4. Spring brake control valve

5. Pressure protection valve

The service relay valve on the trailer is activated by a signal from the:

1. Dash valve

2. Pressure protection valve

3. Quick release valve

4. Foot valve

5. Trailer hand control valve

6. D & E

A two-way check valve takes in two sources of air and

1. Blends the two sources together and delivers them as one

2. Delivers one and exhausts the other

3. Delivers the dominate source

4. None of the above

What acts as the control signal for the spring brake relay valve on a trailer

1. Pressure from the blue knob on the dash valve

2. Pressure from the red knob on the dash valve

3. Pressure from the yellow knob on the dash valve

4. Air form the hand control valve

5. None of the above

When air is put into the parking (or emergency) section of the spring brake chamber it is said to be in the applied condition.

1. True

2. False

In a trailer system the pressure protection valve is used to maintain pressure in the

1. Tank

2. Supply line

3. Service line

4. Brake chamber

5. None of the above

Anti-compounding prevents service brake release and spring brake release at the same time.

1. True

2. False