The Model 734A DC Reference Standard is made up of one 734A-7001 Instrument Enclosure and four 732B DC Standards. The Model 734A-7001 can be purchased separately as needed for your application. The enclosure securely holds up to four 732B DC Standards and/or 732B-7001 External Battery/Chargers (described next). An ac power bus inside the 734A-7001 enclosure powers up to four 732B units with only one ac line cord. Using the enclosure allows you to rack mount 732Bs. Model 732B is a dc voltage laboratory standard that produces reference voltages of 10V and 1.018V. Model 734A contains four 732B DC Standards in a chassis. The 732B is highly stable, rugged and transportable. Its 10V output excels in stability, and can be used as your direct link in the traceability chain to national standards. You can use the 732B 1.018V output to transfer the "volt" at the 1.018V level from one set of saturated standard cells to another. You can also use the 1.018V output as a working standard with older equipment that requires a standard cell voltage input. The 10V output’s long-term stability, predictable drift rate, low uncertainty, convenient level, and immunity to accidental damage make the 732B or 734A the preferred artifact for maintaining a local standard of voltage. With time characterization (Calibration Option 732B-100) the drift rate for the 10V output is given. This reduces the 10V output uncertainty from 2 ppm/year to 1 ppm/year. All outputs of the 732B can withstand short circuit indefinitely, without damage to the instrument or disruption of the state of calibration. Recovery time for a momentary short is less than 2 minutes; for an extended short, recovery time is less than 2 hours. To maintain calibration as a traceable standard, the 732B must continue to receive uninterrupted operating voltage from ac line power or from the internal battery. If battery voltage drops too low, the front panel IN CAL indicator goes out and recalibration is required. The internal rechargeable battery (if switched on) protects the standard from line power interruption and provides power for hot shipment (shipment under power). The 732B outputs are unaffected as you change between battery or ac line power. Battery operation with a fully charged battery lasts at least 72 hours. You can extend battery operation by connecting an external 12V battery such as Model 732B-7001 to the rear panel MONITOR/EXT BAT IN connector. Plugging the 732B into ac line power for 24 hours fully recharges the internal battery. Four front panel indicators show operating status. Model 732B-7001 External Battery and Charger has all but the IN CAL indicator. · AC PWR lights when the 732B is connected to ac line power. · IN CAL goes out to warn you when the 732B may have lost its calibration. This indicator responds to an excessively large drop in battery voltage or a large change in oven temperature. If battery voltage falls below the level needed to keep the 732B working normally, the IN CAL indicator extinguishes, indicating a loss of the state of calibration. Once power is restored and the output has been verified, you can reset the IN CAL indicator. · LOW BAT blinks to warn you to plug the line cord into ac power when only a few hours of battery operation remain. · CHARGE lights when the battery is being recharged in constant-current charge mode, and is off when the battery is charged to the 90% level. At 90% of full charge, a float charge completes and maintains full charge.