1994

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.

FIG. 1
The outline.

FIG. 2
Phantom view showing parts trough one side of PCB.

FIG. 3
Phantom view showing parts trough the second side of PCB.

FIG. 4
This scrambler was semi-duplex like a most handy radiotelephones. The button "push-to-talk" was utilized for switching internal circuit in the scrambler.

FIG. 1
A full-duplex telephone voice-scrambler.

FIG. 2
... after removing a bottom cover. You can see the piggy-back module; the fsk modem and logic.

FIG. 3
Two modules disconnected. The covered by a epoxy-resin elements are uController ST6220 from SGS-THOMSON and two integrated scramblers - PCD4440 from PHILIPS.

FIG. 4
Yet another view. The central button is for activate the scrambler at any time during the telephone conversation. At the right are LED's.

SGS-THOMSON is a registered trademark of SGS-Thomson Microelectronics; now STMicroelectronics. PHILIPS is a registered trademark of Royal Philips Electronics N.V.