This system, which to my knowledge is unique to Landis & Gyr of Switzerland, uses an optically encoded information strip which is embossed into the plastic phonecard.
The card reader verifies the information and burns part of the strip as the credit is used up. Optical cards are free of environmental influences such as magnetic fields and high humidity which makes them ideal for tropical countries.
It is necessary to insert the card into a phone to determine if there is any credit remaining on the card. Mint cards usually come in a sealed pack as proof of being unused
There have been no recorded cases of fraud where this system is in use.
The information strip is usually white allowing easy identification of the value left on the card. However in some cases the strip is the same colour as the remaining card design and it is then necessary to catch the light on the card to see what appears as tracking on the strip area. The more units available, the longer the use indicator.
In some cases such as the Thailand 200 unit cards (left), there are actually 2 strips on the card, one near the top and one near the bottom, each bearing 100 units. These cards are turned upside down to access units 101 to 200.
This is the system with the second greatest number of variants.
The storage of these cards is done on a processor chip which is built into the card. The greatest part of what is visible is the contacts which connect to the chip.
It is necessary to insert the card into a phone to determine if there is any credit remaining on the card. Mint cards usually come in a sealed pack as proof of being unused.
This system, which to my knowledge is unique to Landis & Gyr of Switzerland, uses an optically encoded information strip which is embossed into the plastic phonecard.
