TM  1-1520-240-10            3-2-23 CONTROLS/ INDICATOR FUNCTION line-select switch to return to edit CONTROLS/screen. When complete, press RTN line-select switch to load message into memory and to return to top-level screen. Shutdown Procedures Set function switch to OFF. Gent- ly pull and turn function switch to zeroize. (ZERO) position to erase pre- programmed information, in- cluding all fills. Zeroize func- tion is operational regardless if system is on or off. Emergency Commu- nication The mode used during emer- gencies is determined by the datafill. The equipment oper- ates normally for mode selec- ted. Set mode switch to EM- ER. Press the PTT switch to transmit. If in ALE mode, an ALE call is placed to the se- lected address. Figure  3-2-8.  Control/Display Panel, HF Radio Set (AN/ARC-220) 3-2-25.  Voice Security Equipment TSEC/KY-100. Voice     security     equipment     (TSEC/KY-100),     when installed, provides two-way clear or secure half-duplex voice/data communication for the HF radio system (AN/ ARC-200). Power to operate the TSEC/KY-100 is sup- plied by the No. 2 DC bus through the HF KY-100 circuit breaker located on the No. 2 PDP. 3-2-26.  Controls, Indicators, Connectors and Func- tion (TSEC/KY-100–, Z-AVH)   (fig. 3-2-9) CONTROLS/ INDICATOR FUNCTION MODE Switch Six position rotary switch used to select one of the op- erational modes. PT Plaintext mode. Allows re- ception or transmission of un- encrypted analog voice. EB Emergency Back-up mode. Uses the emergency back-up key to encrypt voice for trans- mission or reception. CT Ciphertext mode. Allows transmission of encrypted voice or data and reception of encrypted or unencrypted voice or data, and non-coop- erative terminal rekeying. RK Remote Keying mode. Per- mits KY-100 to perform auto- matic and manual rekey op- erations. OFFLINE Disables communications and gives access to the sys- tem of menus used to select mode settings, self-test fea- tures, and filling the KY-100 with crypto-variables. Z ALL (PULL) Zeroize mode. Erase all cryp- tographic data stored in the KY-100 except the Emergen- cy Back-up Key. CIK Receptacle Interfaces with a Crypto- graphic Ignition Key which is needed to enable all secure voice and data communica- tions. This function is cur- rently disabled. DSPL/OFF BRT Control Two-function rotary switch which controls the on/off sta- tus and backlight intensity of the LCD display. PNL/OFF BRT Control Two-function rotary switch which controls the on/off sta- tus and backlight intensity for the overall front panel.