amplifies the signal to develop enough motor drive power to steer the receiver head to the azimuth bearing selected on the IRDSC by the operator. Four feedback signals are involved in ensuring the receiver head maintains the correct LOS. An azimuth tachometer signal from the receiver- converter azimuth drive unit is fed back to the mode logic module. The mode logic module produces a gimbal rate signal for the azimuth rate compensation module. An azimuth position signal from the same azimuth drive unit is fed back to the azimuth position compensation module. The mode logic module compares the azimuth position signals with the IRDSC azimuth input and, as applicable, outputs a position error signal to the azimuth rate compensation module. An azimuth gyro rate signal from the receiver-converter’s gyro unit is fed to the azimuth rate compensation module. Also, an azimuth current drive signal is fed back to the rate compensation module. The rate compensation module processes all of the feedback signals (position error, gimbal rate, gyro rate, and current drive signals) and develops an output signal. This output signal, if necessary, maintains the receiver head at the correct selected heading. FORWARD MODE (FWD).— The FWD mode command is processed by the azimuth mode logic module. This module outputs a FWD mode command signal to the azimuth position compensation module. This module will process the command signal. It then outputs a position loop command and a gimbal angle signal to the azimuth rate compensation module. This module then sends an azimuth drive signal to steer the receiver head to 0° azimuth. The azimuth drive signal is amplified by the azimuth heat sink module to produce the motor power to drive the motors in the receiver-converter. The stabilization/positioning feedback circuits work the same as the circuits in the position mode previously explained. MANUAL TRACK MODE.— The manual track mode command signal is processed by the mode logic circuit. This circuit sends a manual track command signal and an azimuth rate inhibit signal to the azimuth rate compensation module. These signals cause the circuits to accept only azimuth rate signals from the target tracking sight control assembly. The TTSC assembly is a pistol grip unit. The operator uses the thumb control on the pistol grip unit to aim the receiver head to the desired LOS. The azimuth drive output signal from the circuit is controlled by the TTSC, and no feedback is used for stabilization. Action of a comparator circuit in the azimuth rate compensation module determines when the receiver-converter gimbals reach their electrical limits and produce limit signals (CW and CCW). These limit signals prevent the manual track mode and computer track mode commands from developing the azimuth drive signal.    The limit signals are fed back to the mode logic module that outputs a CW or CCW signal to the azimuth position compensation module. This signal causes the module to develop an error signal that, in turn, develops appropriate azimuth drive. COMPUTER TRACK MODE.— The aircraft computer supplies gimbal control data bits (azimuth and elevation position rate commands) from its program to the decoder storage module. This module demultiplexes and stores 12-bit azimuth and elevation rate commands. It also provides azimuth and elevation data outputs to the digital-to-analog (D/A) converter module. The purpose of storage is to allow the decoder to output data bits to the D/A converter, while the computer updates itself from feedback information before issuing new gimbal control signals to keep the receiver head at the programmed LOS. When the computer track mode is selected on the IRDSC, the computer track command is processed by the mode logic module. This module will send a computer track mode command to the D/A converter and to the azimuth rate compensation module. The signal enables the D/A converter to process azimuth data bits into analog azimuth position rate signals, which are fed to the azimuth rate compensation module. The D/A converter also sends a computer track mode status signal to inform the aircraft computer that the D/A converter is operating in the computer mode. The computer track command signal enables the azimuth rate compensation module to accept azimuth position rate signals from the D/A converter only. The azimuth rate compensation module disables inputs from the azimuth position compensation module. This means no feedback information can be processed in the computer mode. The rate compensation circuit processes the azimuth position rate signal from the D/A converter and outputs an azimuth drive signal. This signal goes through the azimuth heat sink circuit to slew the receiver head to the azimuth position programmed into the computer. An azimuth resolver in the receiver-converter feeds back four-wire resolver position information signals to the azimuth rate compensation module 6-20