Autelca is a Swiss company and the cards are manufactured not only in Switzerland but in the U.K. and Korea too, and they had been manufactured in Yugoslavia under licence in the years before the war. The cards are magnetic, using the Watermark technology developed by Thorne-EMI, that protects pre-paid telephone cards against skimming, buffering and counterfeit. The first telephones incorporating this technology were first installed during the mid 1980s and has been used in several countries especially during the first years, like many Caribbean islands and African countries, but the system has been discontinued by many telecoms that have preferred other systems like GPT or chip.
The cards have a magstripe of about 11mm along the bottom of the face of the card and early issues used to have information on use on the back. The back is now normally used for illustration but the card still goes into the telephone with the stripe side upwards. The Autelca cards are thinner than GPT but thicker than Japanese cards.