HF FUNCTIONAL DESCRIPTION

Figure 1-13.-TSEC/KY-75 remote control unit. TSEC/KY-75 Remote Control Unit The TSEC/KY-75 remote control unit (RCU) is shown in figure 1-13. This unit enables the operator to operate the security unit without moving from the NAV/COMM station in the aircraft. The following is an explanation of the various controls and indicators on the RCU. 1. 2. 3. 4. ALARM indicator–This indicator will illuminate whenever there is an alarm condition in the security unit. TSEC/KY-75 RCU switch–This switch is not used. PWR/FILL switch–This is a four-position switch used to select the key and storage locations for the various codes used. a b. OFF/ZEROIZE–This position will zeroize all variables stored in the TSEC/KY-75 security unit. To select this position, the operator must pull the knob out 1/4 inch and turn it counterclockwise. This prevents accidental zeroizing during flight. 1, 2, 3–These positions select a particular key for the cipher transmission or reception. They also select the storage area when the key is loaded into the TSEC/KY-75. PWR indicator–This indicator will illuminate white when power is applied to the security unit 5. 6. and the PWR/FILL switch is not in the OFF/ZEROIZE position. SIG CLR switch–This switch is pressed to enable the till operation if the TSEC/KYK-13 or TSEC/KOI-18 is attached If a fill device is not attached pressing this switch will cause the security unit to preamble. FILL connector–This connector connects the filling device to the TSEC/KY-75 security unit electrically. This enables the operator to load keys into the security unit. HF FUNCTIONAL DESCRIPTION Both radio sets function in the same manner; the only difference between the two is the peripheral equipment used. Figure 1-14 shows a system block diagram. Receive Function The RF signal is received by the antenna, coupled through the coupler and the de-energized transmit-receive relay in the RF amplifier, and finally to the receiver transmitter receiver RF input. RF-to-audio conversion is accomplished in the receiver section using inputs from the frequency synthesizer. The recovered audio component is amplified to a power level sufficient to be used as an audio input to the peripheral equipment. Transmit Function During the transmit function, voice or data signals from the peripheral equipment are switched through the COMM switching matrix to the USB and LSB transmit audio inputs to the receiver transmitter. A keying signal is also applied from the peripheral equipment. For emergency or maintenance operations, voice and keying signals can originate at the mic/headset assembly connected directly to the receiver transmitter. Figure 1-14.-HF system block diagram. 1-19