Electrical¶
Electronics¶
Rules found in this domain: P45, P44.
Illustrative, not evidence.
Scenario. A team designs a power supply board for an industrial controller. The board must run on a warm factory floor for years. The team sizes the voltage regulator for the expected peak current, and the board has a backup supply path.
- P44: The team states the design load, the peak current the controller draws, and sizes the regulator above it with a derating factor for the warm floor. A load test at high temperature shows the regulator carries at least that current times the chosen factor.
- P45: The board has two supply paths. In a test the team removes one path at a time, and the controller keeps running on the other. The switch-over circuit is tested as well, because a bad switch would waste the redundancy.
Power grids¶
Rules found in this domain: P45, P47.
Illustrative, not evidence.
Scenario. A regional operator plans how its network survives the loss of a line. When a heat wave pushes demand above supply, the operator has a list of loads to shed in a set order.
- P45: The operator tests the network with each single line out of service. Power still reaches all critical substations, so the function survives the loss of any single element (N-1).
- P47: The operator defines in advance which loads switch off first, such as large interruptible industrial users, and which keep power, such as hospitals. A simulated overload shows the low-priority loads stop first and the critical ones keep running.
Telecom and network¶
Rules found in this domain: P32, P33.
Illustrative, not evidence.
Scenario. A company sends large files between two data centres over several network hops. A fault in a middle router once flipped bits in transit. The company now checks files at the sender and the receiver.
- P32: Integrity can only be fully correct with knowledge at the end points, so the sender computes a checksum and the receiver verifies it. The links in between may also check frames, but only to improve performance.
- P33: The transfer messages that carry each file's name, size and checksum follow a written specification with a machine-checked schema. A message that violates the schema is rejected and logged. The interface states units and time zone explicitly.
Computer engineering¶
Rules found in this domain: P26, P50.
Illustrative, not evidence.
Scenario. A hardware team designs a new embedded processor board. Each block has a scan chain and debug pins. Before layout, the team profiles a benchmark workload on the previous-generation board to see where the time goes.
- P26: Each block has documented test access to set and observe its key states, through the scan chain and debug pins. A tester can drive any block into a known state and read the result.
- P50: The team measures the current constraint, which is memory bandwidth, and names it before any speed-up work. It improves the memory path first, instead of making the already idle arithmetic unit faster.
Broadcast¶
Rules found in this domain: P70.
Illustrative, not evidence.
Scenario. A TV station runs a transmitter site that must stay on air. A feed can look fine on a monitor until the signal suddenly drops out.
- P70: The station measures the signal in real use and alerts on symptoms viewers feel, such as picture freezes and audio loss. Because the output stays clean until the signal collapses (a cliff effect), it also monitors the remaining signal margin.
Microwave¶
Rules found in this domain: P33.
Illustrative, not evidence.
Scenario. Two radio units in a microwave link exchange control messages. One unit reports power in dBm and the other expects watts.
- P33: The interface specification fixes one unit for the power field and puts it in the field name. The receiving unit checks each message against the schema, rejects a message whose power field names the other unit, and logs the rejection, instead of silently accepting it.
Optical (laser safety)¶
Rules found in this domain: Master.
Illustrative, not evidence.
Scenario. A lab builds a setup with a laser. A low-power alignment laser in a closed box needs few controls. A high-power laser in an open lab has a far worse worst case, and its stray reflections are hard to predict.
- Master: The lab scales the rigor to the consequence of failure times the uncertainty. The closed low-power box scores low on both and gets a simple check. The high-power open setup scores high on both: an eye injury cannot be undone, and stray reflections are hard to predict. It gets interlocks, a controlled area, trained staff and a formal review.