---
title: "readAttributeRmsExtremeUnderVoltagePeriodPhaseB(with:)"
framework: matter
role: symbol
role_heading: Instance Method
path: "matter/mtrclusterelectricalmeasurement/readattributermsextremeundervoltageperiodphaseb(with:)"
---

# readAttributeRmsExtremeUnderVoltagePeriodPhaseB(with:)

## Declaration

```swift
func readAttributeRmsExtremeUnderVoltagePeriodPhaseB(with params: MTRReadParams?) -> [String : Any]?
```