Elboxrf received an order for developing voice-scramblers for upgrading ready-made radiotelephones. After a few month of work we designed the range of programmable voice-scramblers. The most advanced unit was dimension of 43x22x6.5mm. It was in form of two-sided PCB with elements on each side. This scrambler was equipped with a voice codec, modem, EEPROM, DC-stabilizer, uController and an programmable socket. It was a real effort to develop schemes for the coding sequence, and for the synchronization algorithm. As a result the voice transmission was undistorted and the very difficult for descramble by unauthorized person. Also synchronization was so fast, that the user does not know that the transmission is coded. This work was very important for the many next Elboxrf's projects. We developed also the CODE-a-PHONE, a full duplex voice-scrambler for telephones.