The PR11 provides a means of phase comparison at the point of paralleling two circuits, without the interposition of voltage transformers or secondary wiring earthed neutral systems. A neon type instrument, it is designed for use on earthed neutral systems up to 11KV. The LLT-PR15D / LLT-PR33D units enable phase angle comparison on earthed neutral systems up to 15KV and 33KV respectively.

The digital reading instruments provide voltage measurements and are supplied with detachable earth lead, allowing the digital leg to be used as a voltage indicator, independently from the phasing leg.