---
title: "readAttributeRmsExtremeUnderVoltagePeriodPhaseB(completionHandler:)"
framework: matter
role: symbol
role_heading: Instance Method
path: "matter/mtrbaseclusterelectricalmeasurement/readattributermsextremeundervoltageperiodphaseb(completionhandler:)"
---

# readAttributeRmsExtremeUnderVoltagePeriodPhaseB(completionHandler:)

## Declaration

```swift
func readAttributeRmsExtremeUnderVoltagePeriodPhaseB(completionHandler: @escaping @Sendable (NSNumber?, (any Error)?) -> Void)
```

```swift
func readAttributeRmsExtremeUnderVoltagePeriodPhaseB() async throws -> NSNumber
```