The 734A DC Reference Standard is a four-cell direct voltage reference used to maintain the volt in primary and secondary calibration laboratories. The unit consists of 4 each 732B's which are independent and battery operated. Statistical methods can be used to reduce the uncertainty of the 734A outputs. The long term stability, drift rate, and low uncertainty of the 10 volt outout allows direct substitution for saturated standard cells in many cases. Four independent outputs of 10 V and 1.018 V are available. Stability is .3 ppm/month or 2 ppm/year.