Upon completion of this chapter, you should be able to:
1. Compare standard synchro system connections with IC synchro connections.
2. Describe the operation of a step transmitter and receiver, and list the advantages and
disadvantages of a step-transmission system.
3. Compare the construction and operation of a resolver to those of a transformer, describe the
solution of resolution and composition problems by a resolver.
Some other devices that logically should be included in this module are the IC synchros, step motors,
and resolvers. These are all electromagnetic devices used in various shipboard and aircraft applications.
They can be considered as second cousins of the synchro.
The engine order telegraph, steering telegraph, rudder-angle indicator, and similar position-
indicating systems used on naval ships are usually simple synchro systems. Some ships, however, use IC
synchros to transfer such information. These units operate on the same general principle as the synchros
we discussed in chapter 1.
The interior communication synchro (IC synchro) is gradually being phased out and replaced by
standard synchros when replacement is required. However, you will still find some IC synchros in use
today. For that reason, you will find some background information on their purpose and theory to be
beneficial. We will present these synchros in very basic form in the following paragraphs.
Because of their construction, IC synchros are sometimes called reversed synchros. The primary
winding, consisting of two series-connected coils, is mounted physically on the stator. The secondary,
consisting of three Y-connected coils, is mounted physically on the rotor. This is shown schematically in