depending upon the direction of rudder shaft displacement from zero. Both signals would be 
mixed with other readout data and transmitted over the common radio link. 
The console contains all circuitry for using this type of rudder position readout. The 
output of the rudder channel discriminator is used to drive a squaring and frequency-doubling 
circuit. The output of this circuit may be used to drive an external digital indicator and re- 
cording system with rudder position displayed to the nearest tenth of a degree. The tone 
circuitry would be used to operate a port-starboard indicator or marker. Standard digital 
events-per-unit-time meters and recorders may be operated from this circuitry. 
For console indication the output of the squaring and frequency-doubler circuit is used 
to drive a pulse-rate-to-current converter. The output of the converter is applied to the 
RUDDER ANGLE indicator. Meter polarity is automatically reversed by the tone circuitry as 
the rudder is moved from port to starboard positions. 
5.1.2 Rudder Running Time 
The rudder running-time circuit control signal is obtained from the output of the 
tachometer generator in the servo system. The output of the tachometer is applied to. an 
amplifier which drives a sensitive relay. A gain control in the amplifier is used to select the 
velocity at which relay operation takes place. One set of relay contacts is brought out to a 
connector on the model-borne readout unit for control of lamps used when the model ships are 
tracked photographically. Another set of contacts is used to turn a tone ON which is trans- 
mitted to shore over the common radio link. 
In the console, a tone detector circuit separates the running-time signal from the 
other tones and operates a relay which controls current to the clutch of an electric clock 
mounted on the rudder control panel. 
The overall accuracy of this system is somewhat limited because of the number of 
electromechanical delays. Accuracy is also affected by the run-in rate of the servo and the 
setting of the amplifier gain control. However, under most conditions, rudder running time 
will be indicated to within 0.1 second or better. 
5.2 RPM CIRCUITS 
The two channels of propulsion shaft rpm circuitry are of nonstandard design in 
order to achieve a higher degree of accuracy and stability than is possible by the standard 
FM-PM telemetering technique. Both channels are identical except for choice of subcarrier 
frequency. 
The rpm pickup consists of a small aluminum wheel with five soft iron inserts and an 
E-core pickup mounted in a yoke attached to the shaft of the wheel by ball bearings. The 
shaft is hollow and designed to clamp onto an intermediate 5/16-inch-diameter propulsion shaft. 
The yoke is fastened to the model hull by a thin strap and holds the E-core coil at a fixed 
distance from the surface of the wheel. 
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