The coil of the E-core assembly is connected to a reactance-controlled subcarrier 
oscillator. The coil and capacitors within the oscillator unit form the tank circuit of an 
oscillator. As the wheel is rotated, the inductance is varied, causing a change in subcarrier 
frequency. The subcarrier output is then mixed with the other subcarrier signals and trans- 
mitted to the console where it is separated from other readout data by the discriminator. 
The discriminator output is a variable low-frequency voltage whose frequency is pro- 
portional to shaft rpm. The signal frequency is doubled and then shaped into a rectangular 
wave. The output of the shaping circuit may then be used to drive an external indicating- 
recording system such as the TMB Revolutions-Speed-Time Recorder Type 223 or a standard 
events-per-unit-time indicator and recorder. 
The output of the pulse shaper is also used to drive a pulse-rate-to-current converter 
stage where current output is proportional to pulse-input rate to an accuracy of better than 
1 percent. This current is used to drive the rpm meter on the console. Full-scale ranges 
0—1500 or 0—3000 rpm for both channels may be selected by a switch on the propulsion 
control panel. 
5.3 SPARE ANALOG CIRCUIT 
A spare analog circuit is included in the telemetering link. The spare receptacle in 
the readout unit is wired for an Electro-Mechanical Research Model 94 potentiometer-controlled 
subcarrier oscillator. The console end of the link is wired for a spare Tele-Dynamics, Inc. 
Type 2201C Demultiplexer.* The output is connected to the 1-0-1 milliampere meter on the 
console marked SPARE, and also to an output connector which can supply + 1.0 milliampere 
to an external load. 
5.4 SPARE TONE CIRCUIT 
Connections are included in the readout unit for a spare tone channel. The circuit is 
operated in the model by the closing of external contacts which turn on the tone. It is relayed 
to shore via the telemetering link and is there used to operate a set of single-pole double- 
throw relay contacts which are available at a connector on the console. System response time 
is limited to about 0.1 second by the operating time of the relays and tone detector circuitry. 
6. POWER SUPPLIES 
6.1 CONSOLE EQUIPMENT 
The power supplies for all console equipment are mounted in two chassis at the rear 
of the console. Power supplies for all control circuitry are constructed in the smaller chassis 
*Trade name for discriminator. 
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