Voting equipment TESLA HZ-600 was developed by TESLA VÚST in seventies of the last century. This multiplexed, two-way voting system used two frequencies in longwave and VHF for addressing the individual clinet's box and for transmitting the information about the vote - in the other words, if the red or green button is pressed. This system, originally developed for the National Assembly of ČSSR was never used routinely. Although, the smaller, scaled down sets were used for TV shows and other nonofficial purposes with a success.
The author is looking for any documentation, witness info etc.