Note that prestandard size 1 is approximately the same size as standard size 23 (2.21 to 2.30 inches
in diameter). Prestandard size 3 is approximately the same size as standard size 31. Prestandard size 5 is
approximately the same size as standard size 37.
The letters used in the prestandard coding system indicate the function, mounting, or special
characteristics of the synchro as shown in the following chart.
Flange Mounted Receiver (this letter is normally omitted if letters
other than H or S occur in type designation)
Bearing Mounted Unit
Nozzle Mounted Unit
Navy prestandard synchros are rarely used today. They have been replaced by the standard synchro.
However, by being familiar with the prestandard coding system, you will be able to identify the older
synchros and make correct replacements if necessary.
Q-6. What does the code 26V-11TX4D mean on a synchro nameplate?
Q-7. Which of the two synchro designation codes is indicated by 5DG on a synchro nameplate?
Schematic symbols for synchros are drawn by various manufacturers in many different ways. Only
five symbols (as shown in figure 1-3), however, meet the standard military specifications for schematic
diagrams of synchros and synchro connections. When a symbol is used on a schematic, it will be
accompanied by the military abbreviation of one of the eight synchro functional classifications (TR, TX,
The symbols shown in views A and B of figure 1-3 are used when it is necessary to show only the
external connections to a synchro, while those shown in views C, D, and E are used when it is important
to see the positional relationship between the rotor and stator. The letters R and S, in conjunction with an
Arabic number, are used to identify the rotor and stator connections; for example, R1, R2, S1, S2, and S3.
The small arrow on the rotor symbol indicates the angular displacement of the rotor; in figure 1-3 the
displacement is zero degrees.