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LEARNING OBJECTIVE Recall the purpose and advantage of synchros in naval ordnance equipment.

Synchro is the name given to a wide variety of position-sensing devices used to convert mechanical signals to electrical signals or to convert electrical signals to mechanical signals. The name synchro comes from the word synchronize that means "to happen or take place at the same time." All synchros are self-synchronous; hence, the name is most descriptive of their basic action.


The purpose of synchros is the precise and rapid transmission of data among equipments and stations. The change in course, speed, and range of targets, and the changes in the position of the ship in relation to the position of the target must be acted upon in a minimum of time. Speed and accuracy of data transmission are most important. Without the position-sensing device known as the synchro, the offensive and defensive capability of the fleet would be greatly limited. Navy ships rely on synchros for rapid data transmission within weapons systems in such equipments as computers, faze setters, sight setters, guns, and missile launchers. Gun and GMLS system power drive controls make extensive use of synchros.


The flexibility of synchros over mechanical mechanisms, such as gearing and shafting, gives them marked advantages; for example:

The controlling unit can be along distance from the controlled unit.

Any obstacle in the path can easily be bypassed by leading connecting wires around it.

l The synchro system uses very little electrical

power and eliminates the necessity of mechanical linkages between widely separated units.

Besides the advantages of using synchros over mechanical mechanisms, there are other advantages:

They provide continuous, accurate, and visual reproduction of important or need-to-know information between widely separated stations.

They have good reliability, requiring minimum maintenance.

They are small in size, providing a significant saving in space and weight.

They have a wide adaptability without sacrificing precision.

Synchro systems are important in the ordnance field in controlling naval weapons because of their accuracy and speed. Experience with naval weapons control and operation of ordnance readily proves the importance of the synchro mechanism. A point to remember is that naval weapons controlled from remote stations must use synchro systems for their control. A well-placed shot can save many lives, and the accuracy of a weapon depends upon the correct operation of the synchro system.

Classification of Synchros

Synchros work in teams. Two or more synchros interconnected electrically form a synchro circuit. Basically, synchros can be divided into three classifications: (1) transmitters, (2) receivers, and (3) differentials.

The synchro transmitter is located at the controlling station; its output is an electrical order signal. These synchros were originally called synchro generators but are now functionally classified into two types: (1) torque transmitter (TX) and (2) control transmitter (CX).

Torque and control transmitters are mechanical y identical. However, the types of systems in which they are used differ. Torque transmitters are used in systems that require a mechanical output (dials, etc.), while control transmitters are used in systems that require an electrical output.

The synchro receiver is located at the station being controlled, and its output can be either electrical or mechanical, depending on the type of synchro used. These synchros are functionally classified into the following types: (1) torque receiver (TR) and (2) control transformer (CT).

Torque receivers are used where the rotors must perform a mechanical function, such as positioning a dial or valve. The main difference between torque receivers and torque transmitters is in their rotors. Rotors of torque receivers have a damper, while rotors of torque transmitters do not. Torque receivers were originally known as synchro motors.

Control transformers are used where an electrical signal output is required. It is safe to say that all power drives controlled by amplifiers also have control transformers.

The synchro differential is used to add or subtract two signals and to transmit the result either to another synchro or as a mechanical output. In either case, the differential can always be identified by its rotor (R) leads. All other synchros have only two rotor leads while the differential has three. Functional y, differentials are classified as (1) torque differential transmitter (TDX), (2) control differential transmitter (CDX), and (3) torque differential receiver (TDR).

A mechanical device known as an inertial damper is used to prevent oscillation or spinning when the rotor of the torque synchro receiver turns in response to a sudden change of a received signal. The most common type of inertial damper consists of a heavy brass flywheel that is free to rotate around a bushing attached to the rotor shaft. A tension spring on the bushing rubs against the flywheel so that they turn together during normal operation. If the rotor shaft tends to change its speed or direction of rotation suddenly, the inertia of the damper opposes the changing conditions, and the resulting friction between the spring and the flywheel dampens the tendency to oscillate. Because of the inertia damper, torque receiver and transmitter synchros are not completely interchangeable; a receiver may be used as a transmitter, but a transmitter is not suitable for use as a receiver.

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