Installation Information for ST-20BK or ST-25BK Series interfaced to Kenwood TK-790 with or without control head (This is a Direct Plug-in installation) General Information: This Direct Plug-in application applies to the Selectone ST-20BK simple ST-20BK: frequency domain inversion scrambler operating with Kenwood TK-790. The cipher process inverts speech frequencies in reference to one of eight possible inversion carriers. The scrambled speech is unintelligible to the casual listener, but the recovered audio is very clear. Operation is virtually transparent to the user. The Clear/Cipher input, used to enable or disable the cipher mode, is the only user control. Applications include commercial shared repeaters and other business and marine radio systems where protection is desired from co-channel users and casual eavesdroppers. The ST-20BK does not require a license for export. This Direct Plug-in application applies to the Selectone ST-25BK Rolling ST-25BK: Code Voice Encryption unit operating with Kenwood TK-790. The ST-25BK Rolling Code Encryption Module is a miniature, high security voice encryption device with up to four user programmable code keys, each selected from over four billion possible keys, may be used to communicate in a secure mode with up to four different groups on the same radio channel. To insure security, code keys are stored in a non-volatile EEPROM and are never transmitted over the air. The Clear/Cipher select line is the only user control. Receive mode is automatic, so that clear speech or encrypted speech with the proper code key will be received regardless of the mode selected. Programming is accomplished via the ST-954B pig-tail programmer which plugs into a computer serial port. All software is available free at www.selectone.com. Technical Information: General: The installation will require plugging in the ST-20BK or ST-25BK into the interface cable P/N (xxx-xxxx) then into the Kenwood TK-790 mobile radio. The radio will require modification of the RX and TX audio path. ST-25BK only, optional (white/orange) wire if transmit alert tone is required. The transmit alert tone is required when a long transmit delay is need to gain access to a system such as (LTR). This will alert the user with a beep that the delay time has expired and is ready for the user to go ahead and talk. Operation: This application uses the programmable OPT key to enable clear/cipher mode by a single push. On the display will appear the (OPT) indicator as well as an audible single beep in the speaker, this is an indication that you are now in the ciphered mode. Press it again the displayed (OPT) indication will disappear and you will hear two audible beeps, you are now in the clear mode. Press and hold the (OPT) key to enter the code setting mode. Codes 1 to 16 will be displayed. Set a code by turning the [Up/Down] knob. When the OPT key is pressed again, the code setting mode terminates. Installation Requirements: Experienced technician with radio and encryption experience. Radio service manual. Radio Service Monitor. Soldering Iron and required hand tools. ST-954B programmer and ST-25BPM software. (ST-25BK ONLY) Kenwood TK-790 programming software and adapter. PC compatible computer. ST-25BK Configuration: See below (St-25BK Programming Parameters) Installation Information: Refer to the Wiring Connection Chart & NOTES and Radio Programming. Modification Instruction for TK-790: Remove R515 and R604. Modification Instructions for ST-20BK and ST-25BK series: Insert and solder a 1K resister into R28 and R35 customer select locations. ST-25BK Programming Parameters Wiring Connection Chart & NOTES for the ST-25BK to Kenwood TK-790 Remove the upper half of the case of the TK-790. NOTES: Radio: 1. Remove R515 and R604 on the control unit. ST-20BK or ST-25BK: 2. Add a 1K resister in the customer select resistor location of R28 and R35. ST-25BK only: 3. OPTIONAL, this connection should only be used when a long transmit delay is needed. Transmit alert tone is a courtesy beep to indicate go ahead and talk. Add a 1.2m ohm resister in series with the WHITE/ORANGE lead. INSTALLATION: Plug one side of ST-20BK or ST-25BK interface cable P/N xxx-xxxx into the ST-20BK or ST-25BK and the other side into CN508 of the Kenwood TK-790. Cover the ST-20BK or St-25BK with the protective shrink sleeve the secure the encryption with the doublesided tape to the open flat area of the TK-790. J1 ST-20/25BK PIN # COLOR 1. BLUE 2 WHITE/YELLOW 3. RED 4. WHITE/ORANGE 5. WHITE/GREEN 6. GREY 7. VIOLET 8. N/A 9. BLACK 10. WHITE/RED 11. GREEN 12. ORANGE 13. YELLOW ST-20/25BK Interface Cable P/N xxx-xxxx ST-20/25BK FUNCTION RECEIVE AUDIO OUTPUT CODE SELECT 1 INPUT POSITIVE (+) SUPPLY SPEAKER BEEP OUTPUT CODE SELECT 2 INPUT PTT IN INPUT CLEAR/CIPHERED INPUT AMP ENABLE (NOT USED) OUTPUT NEGATIVE (-) SUPPLY CODE SELECT 3 INPUT RECEIVE AUDIO INPUT TRANSMIT AUDIO INPUT TRANSMIT AUDIO OUTPUT CN508 RADIO TK-790 PIN # FUNCTION 3. DEI 8. BC4 13. 8C OPTIONAL CN507-8 (SEE NOTE 2) 7. BC3 12. PTO 4. AC N/C 14. E 6. BC2 11. DEO 2. MCO 1. MCI Required Radio Programming for TK-790 Mobile Radio To enable Scramble feature on your radio, you must first set it up through the initial radio setup. To do this run the radio programming software, go to Model, set all your features. When you come to Voice Scrambling choose YES. Next we must set a button to enable and disable the scrambler. Go to EDIT, then Key Assignment, then choose Panel Switch Assignment. Select the switch you wish to use then assign it the OPT key. Required Radio Programming for TK-790 Mobile Radio Continued At the main menu press F10 to edit channel. In the Voice Scrambler location you must assign each channel you wish to scramble with a power-up code select number.
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