Resistor with taps equally spaced Lock switches Rotatable contact Resistor + − Indicating element Transmitter Indicator Transmitter 26V. 400 Hz AC Electro- magnetic rotor Stator windings Indicator pointer 26 volts 400 Hz power supply A B C D N S A B C D N S Up Down Indicating magnesyn Transmitting magnesyn Soft iron core Toroidal winding Permanent magnet $^{1}$/3 $^{1}$/3 $^{1}$/3 Figure 10-50.  An autosyn remote-indicating system utilizes the  interaction between magnetic fields set up by electric current flow  to position the indicator pointer.  Figure 10-49.  A magnasysn synchro remote-indicating system uses  AC. It has permanent magnet rotors in the transmitter and indictor.  Figure 10-48.  A lock switch circuit can be added to the basic DC selsyn synchro system when used to indicate landing gear position and  up- and down-locked conditions on the same indicator.  Autosyn systems are further distinguished by the fact that  the transmitter and indicator rotors used are electro-magnets  rather than permanent magnets. Nonetheless, like a permanent  magnet, an electro-magnet aligns with the direction of the  magnetic field created by current flowing through the stator  coils in the indicator. Thus, the indicator pointer position  mirrors the transmitter rotor position.  [Figure 10-50]  AC synchro systems are wired differently than DC systems.  The varying current flows through the transmitter and indicator  stator coils are induced as the AC cycles through zero and the  Aircraft with alternating current (AC) electrical power  systems make use of autosyn or magnasysn synchro remote  indicating systems. Both operate in a similar way to the DC  selsyn system, except that AC power is used. Thus, they  make use of electric induction, rather than resistance current  flows defined by the rotor brushes. Magnasyn systems use  permanent magnet rotors such as those found in the DC  selsyn system. Usually, the transmitter magnet is larger than  the indicator magnet, but the electromagnetic response of the  indicator rotor magnet and pointer remains the same. It aligns  with the magnetic field set up by the coils, adopting the same  angle of deflection as the transmitter rotor.  [Figure 10-49]  10-28 AC Synchro Systems