1-5 Table 1-1.—Synchro Information FUNCTIONAL CLASSIFICATION ABBREVIATION INPUT OUTPUT Torque transmitter TX Mechanical input to rotor (rotor energized from AC source) Electrical output from stator representing angular position of rotor to TDX, TDR, or TR. Control transmitter CX Same as TX Same as TX except it is supplied to CDX or CT Torque differential transmitter TDX Mechanical input to rotor, electrical input to stator from TX or another   TDX. Electric output from rotor representing algebraic sum or difference between rotor angle and angle represented by electrical input to TR, TDR, or another TDX. Control differential transmitter CDX Same as TDX except electrical input is from CX or another CDX. Same as TDX except output to CT or another CDX. Torque receiver TR Electrical input to stator from TX or TDX. (Rotor energized from AC source) Mechanical output from rotor. Note:  Rotor has mechanical inertia damper. Torque differential receiver TDR Electrical input to stator from TX or TDX, another electrical input to rotor from TX or TDX. Mechanical output from rotor representing algebraic sum or difference between angles represented by electrical inputs. Has inertia damper. Control transformer CT Electric input to stator from CX or CDX, mechanical input to rotor. Electrical output from rotor proportional to the sine of the angle between rotor position and angle represented by electrical input to stator. Called error signal. Torque receiver TRX Depending on application, same as TX. Depending on application, same as TX or TR. Synchros are also classified according to their operating frequency. This classification was brought about by the development of the 400-Hz synchro. Prior to this time, the 60-Hz synchro was the only one in use. Synchro operating frequencies are covered in detail in the section on synchro characteristics. Q-3.   Name the two general classifications of synchro systems. Q-4.   What is the difference between a torque synchro and a control synchro? Q-5.   Using table 1-1, name two synchros that provide a mechanical output. STANDARD MARKINGS AND SYMBOLS Synchros used in the Navy can be grouped into two broad categories: MILITARY STANDARD SYNCHROS and PRESTANDARD NAVY SYNCHROS. Military standard synchros conform to specifications that are uniform throughout the armed services. New varieties of equipment use synchros of this type. Prestandard synchros were designed to meet Navy, rather than servicewide, specifications. Each category has its own designation code for identification.