Figure 2-3.--Phantom view of a synchro.

in 5-knot intervals from 0 to 100 knots, covering 360.

A revolving pointer directly attaches to the shaft.

The dials and pointers are illuminated by red lights.

No lamps in parallel supplied from a 115/6-volt

transformer inside the housing provide dial illumination

for each assembly. A knob on the side of the case controls

a rheostat for varying the intensity of the illumination.

If the dials are indicating inaccurately, and you

decide to orient the speed and direction dials to a

different position, it will be necessary to zero the

Figure 2-4.--A simple synchro system.

synchros after the dials are repositioned. Zeroing

synchros is discussed later in this chapter.

Synchros (fig. 2-3) are used primarily for the rapid

NOTE: The type B indicator does not have dials that

and accurate transmission of information between

can be repositioned. Consider this fact when mounting

equipment and stations. Synchros are seldom used

the component.

singly. They work in teams, and when two or more

synchros are interconnected to work together, they form

The synchros in the indicator, either a 18TRX6 or

a synchro system. Such a system may, depending on the

18TRX4, electrically connect to the synchros in the

types and arrangement of its components, be put to

transmitter. The synchros in the indicator assume the

various uses. Figure 24 shows a simple synchro system

positions dictated by the transmitter synchros. The

that can be used to transmit different types of data.

pointers fastened to the rotor shafts of the synchros

indicate wind direction and windspeed on separate

STANDARD SYNCHRO CONNECTIONS

circular dials.

In systems in which a great many synchro units are

used, it is necessary to have a closely defined set of

SYNCHROS

standard connections to avoid confusion. The conven-

tional connection is for counterclockwise rotation for an

In performing the required PMS and maintenance

increasing reading.

on wind direction and indicating systems and on synchro

signal amplifiers (discussed later in this chapter), you

The standard connections of a simple synchro

should have an understanding of synchros. The follow-

transmission system consisting of a synchro transmitter

ing paragraphs will discuss synchros and the zeroing of

and receiver is shown in figure 2-5. The R1 transmitter

synchros.

and receiver leads connect to one side of the 115-volt ac

supply line. The R2 transmitter and receiver leads con-

nect to the other side of the line. The stator leads of both

the transmitter and receiver connect lead for lead; that

is, S1 connects to S1, S2 to S2, and S3 to S3. Thus, when

sending an increasing reading over the transmission

system, the rotor of the synchro receiver will turn in a

counterclockwise direction.

When it is desired, the shaft of the synchro receiver

turns clockwise for an increasing reading. The R1 and

R2 transmitter and receiver leads connect as before. The

S1 transmitter lead connects to the S3 receiver lead, and

the S2 transmitter lead to the S1 receiver lead.

ZEROING SYNCHROS

If synchros are to work together properly in a

system, they must be correctly connected and aligned in

respect to each other and to the other devices with which

Figure 2-3.--Phantom view of a synchro.

they are used. The reference point for alignment of all

2-4