PART IV — MAINTENANCE 
1. DISCUSSION 
The Type 304 Radio-Control System is composed of a group of commercially and 
specially designed units. The standard commercial items used in the system are (1) 
subcarrier oscillators, (2) telemetering transmitters, (3) telemetering receivers, (4) subcarrier 
discriminators (demultiplexers), and (5) transistor regulated power supplies. The motor- 
alternator, motor-generators, nickel-cadmium batteries and the battery charger are commercial 
units manufactured or packaged according to Model Basin specifications. All other units are 
of special design to meet system requirements. The maintenance of the transmitter, receiver, 
and subcarrier discriminators is fully described in manuals supplied by the manufacturers. 4 5»© 
All circuitry used in special units of the system is of straightforward design but many 
of the adjustments in these circuits are critical if optimum system performance is to be 
maintained. The control and readout sections of the system may be treated as separate 
systems except for common chassis ground and power input connections. In most cases it 
will be possible to isolate trouble to a specific channel or unit by means of the blown fuse 
indicators, the power supply test meter in the console, the power supply test points in the 
model equipment, or the meters on the discriminators in the model or shore equipment. Adjust- 
ments should not be made to the internal controls unless proper test equipment is available 
for checking the effect on the system. It should be noted that it will be necessary to com- 
pletely check the calibration of units such as the subcarrier oscillators and discriminators 
if tubes are changed. It is suggested that personnel performing maintenance on the 
telemetering circuitry use ‘‘The Theory and Application of FM-FM Telemetry’’? 
as a guide 
to circuit setup and testing. 
The following sections of this part of the report describe precautions to be taken when 
replacing components and the procedures to be followed in making adjustments. 
2. TELEMETERING EQUIPMENT 
The general alignment and maintenance procedures for the transmitters, receivers, and 
discriminators are described in instruction manuals supplied by the manufacturer.4°5°© The 
adjustments described in the following paragraphs are those which are not described in the 
manufacturers’ literature, or are unique to this system. 
