The described apparatus is a versatile bridge circuit with the following key features: l Ratio Arm: Two dials with selectable resistances of 1, 10, 100, and 1000 ohms. l Resistance Arm: Three dials providing decade resistances of 0.1, 1, and 10 ohms. l Slide Wire: A calibrated wire with 0.17-ohm total resistance, divided into 170 equal parts for precision adjustments, connected in series with the unknown inductance.