5. READOUT EQUIPMENT 
A limited amount of data readout equipment has been included in the radio-control 
system. This is to guide the console operator in maneuvering the model and to supply a 
continuous check on proper behavior of the control circuitry. The system is designed so that 
the telemetering link may be expanded in the event that additional analog data channels are 
required. 
The system includes circuitry for console indication and external recording of rudder 
position, two channels of propulsion shaft rpm, and one spare data channel. The running 
time of the rudder servo is indicated on a clock on the console. One spare ON-OFF tone 
channel is also included for operation of auxiliary equipment. All readout circuitry is arranged 
so that the data may be recorded on equipment currently in use at the Model Basin. 
5.1 RUDDER CHANNEL 
5.1.1 Rudder Position 
The rudder servo unit contains a 5000-ohm center-tapped potentiometer which is 
coupled directly to the output shaft of the servo. The readout circuitry is arranged so that 
either analog or digital data transmission may be used. 
5.1.1.1 Analog Readout. The analog method, for which all equipment is furnished, 
is a simple subcarrier circuit. The potentiometer is used to control the frequency of a sub- 
carrier oscillator. This signal is mixed with other subcarrier signals and is transmitted over 
a common radio-frequency link. The signal is received at the console and separated from the 
other subcarrier signals by the rudder channel discriminator. The output of the discriminator is 
connected to the RUDDER ANGLE meter on the console panel and to a connector for operation 
of an external recorder requiring + 1.0 milliampere or less. 
5.1.1.2 Digital Readout. The second method of rudder position readout is for use 
when greater accuracy and elimination of telemetering system drift is mandatory. In this 
system, rudder position data is converted to digital form in the model, thereby eliminating the 
effects of drift and nonlinearity in the telemetering link. All equipment is furnished for this 
system except the analog-to-digital converter. In the system recommended in the original 
specification,? a velocity-controlled servo would generate a train of rectangular waves with 
the rate proportional to the displacement of the rudder shaft potentiometer from the 0-degree 
position. The output frequency would be 5 cycles per second per degree of rudder offset. An 
alternate system would be to use a very accurate voltage-to-frequency converter similar to the 
Dymec Inc. Model DY-2210 with the output rate reduced to the aforementioned value. The 
output of either of these systems would be used to modulate a voltage-controlled subcarrier 
oscillator. A microswitch mounted on the rudder servo unit turns a tone channel ON or OFF 
II-9 
