236 NAVIGATIONAL COMPASSES
The terminals of the amplifying circuit and the line Z, Fig. 189, are joined to the terminals of a three-phase reversing motor M, Fig. 178.* By these means, the hollow sphere is turned till the followup electrodes are in the equilibrium position, that is, till the northsouth line of the compass card is in the geographic meridian. The same lines operate repeater compasses, a course recorder, an automatic pilot, or other repeater devices.
§6. The Arma Gyro-Compass
142. The Sensitive Element. - The Mark IV Model 1 gyrocompass made by the Arma Engineering Company of Brooklyn, New York, Fig. 190, has two gyros capable of precession about