Practice question

Readouts displayed by the EOT and HTD must not differ by more than how many PSI to meet two-way requirements?

  1. Three PSI.
  2. One PSI.
  3. Five PSI.
  4. Ten PSI.

Answer: A — Three PSI.

The readouts from the End of Train device and the Hand Throttle Device must stay within a small tolerance to ensure both devices are reporting the same brake status. The limit is three PSI, which accounts for normal variations in sensor accuracy, transmission, and slight timing differences when brakes are applied or released. Keeping differences within this 3 PSI range helps prevent misinterpretation of brake conditions and ensures reliable two-way communication. A difference of one PSI is typically too strict for practical operation, while five or ten PSI would allow larger discrepancies that could hide real changes in brake status and create safety risks.

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