Pharmacogenetics of tardive dyskinesia in schizophrenia: The role of CHRM1 and CHRM2 muscarinic receptors. Boiko, A. S., Ivanova, S. A. Three phase energy meter. • Class 1 (kWh) according to EN • Class B ( kWh) according to EN • Accuracy ±% RDG (current/voltage). The Cumulative Electric Usage Display shows your cumulative usage in kilowatt- hour (kWh) up to your current billing period. Your Retail Electric Provider uses.