(b)  
The TMSP transmitter circuits inform the TMC of mode, derating factor, and assumed temperature selection. Data is transmitted as a single 32-bit digital word called the REQ MODES (request modes) word. The REQ MODES word informs the TMC of TMSP power status, mode switch selection, and TEMP SEL switch position. The REQ MODES word is transmitted to the TMC every 16 milliseconds.

 (c)  
The clock generator circuit card consists of a crystal-controlled oscillator that generates a 2 MHz signal. The 2 MHz is divided to form 16 millisecond clock pulses used by the TSMP. The clock triggers the sequence of events required to transmit the 32-bit REQ MODES word.

 3. Operation
_________
 A. Functional Description
 (1)  Thrust Management System TMS Power Distribution (Fig. 7)
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MAINTENANCE MANUAL

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(a)

(b)

(c)

(d)

757 MAINTENANCE MANUAL
TMC Power
 1)  The TMC power consists of 115v ac and 28v dc power. The 28v dc standby bus provides power for disconnect warning if TMC power fails. The TMC excitation relay connects 115 vac power and 36 vac control signals to the servomotor when engage conditions are valid. The EMI filters remove transients from the line and internal switching noise from the power supply.
 2)  The 115v ac aircraft power is transformed to appropriate levels in the TMC. The 8v ac is used for TMC demodulation/modulation reference, and 26v ac is used for PLA transducer excitation. Full wave rectification provides |15v dc and +5v dc for TMSP internal power. The TMC provides voltage regulation on all dc outputs.
 3)  The power supply is monitored to provide a primary power fail discrete that results in a TMC INVALID when input power is low. The abnormal steady-state ac limit is 97v ac and the dc lower limit is 18v dc. The TMC is also monitored to provide a power fail discrete if the |15v dc or +5v dc logic supply falls below |14v dc or +4.5v dc, respectively.
TMSP Power
 1)  The TMSP receives +5v dc from the TMC. In order to maintain this voltage within |0.25v dc under varying conditions, remote sensing lines are provided (+5 volts sense and ground sense). When +5 volts changes, the TMC power supply/regulator responds, thus ensuring that normal operating limits are maintained. When the voltage drops below +4.3 volts, the TMSP power loss monitor provides a TMSP status fail signal to the TMC. The TMC also provides |15v dc power that operates the TMSP transmitter.
A/T Servomotor Generator
The A/T servomotor generator has two main components:
 -
A two-phase motor that moves the throttles as commanded by the TMC

 -
A single phase generator (or tachometer) which provides servo rate feedback to the TMC.

 1)  The servomotor has a fixed field winding which uses 115 vac excitation and two control windings which use 36 vac excitation (provided by the TMC servo power amplifier). The servomotor drives at a rate proportional to the pulse width of the control voltage. Both excitation voltages are controlled by the TMC excitation relay.
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MAINTENANCE MANUAL

 2)  The tachometer is an AC generator that uses 115 vac excitation. The tachometer output is a linear relationship between shaft rpm and AC output voltage. The excitation voltage is directly connected to airplane power.
 (e) A/T ARM
 1)  The A/T ARM switch is on the MCP. When positioned to ARM, the A/T switch connects 28 vdc to arm the excitation relay.
　
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