A D-C telemeter or D-C Selsyn for aircraft

A SIMPLIFIED concept of the operation of the d-c Selsyn may be obtained by referring to Figure 1 which shows a coil wound on a toroidal iron core. This is a continuous single layer winding with two brushes supplying direct current at diametrically opposite points. It is evident that a magnetic pole will be set up in the core under each of the brushes, and that the magnetic field inside the core will be as shown. This field will follow the brushes as they are rotated. If a polarized permanent magnet rotor is placed inside the core, it will revolve so as to keep its direction of magnetization in line with the brushes.