The Vanguard Turns Ratio Calibration Standard features three decade rotary switches (unit, 10th, and 100th) for selecting the turns ratio. A multiplier switch provides  1, 10, 100, 200, 1000, and 3000 multiplier values.

The unit uses a nickel-iron supper-alloy core toroidal transformer to ensure a very low excitation in order to achieve high turns ratio accuracy. Up to 250Vac test voltage can be used with the Vanguard Turns Ratio Calibration Standard. The high excitation test voltage allows the unit to be used with virtually all turns ratio testers on the market.