their name from optical structure embossed inside the cards. This optical structure is heated and destroyed after use of the units. Visible marks are left on the top of the cards, so that the user can see the balance of remaining units. Optical cards were produced by Landis+Gyr and Sodeco from Switzerland and were popular early phonecards in many countries with first optical phonecards successfully introduced in 1977 in Belgium. Such technology was very secure and not easily hackable but chip cards phased out the optical phone cards around the world and the last Landis+Gyr factory closed in May 2006 when optical phonecards were still in use in few countries like Austria, Israel and Egypt. The third system of stored-value phone cards are smart cards and use an embedded microchip. These were first launched on a large scale in 1986 in Germany by Deutsche Bundespost after three years of testing, and in France by France Télécom. Many other countries followed suit, including Ireland in 1990 and the UK circa 1994–1995, which phased out the old green Landis+Gyr cards in favor of the chip (smart) cards. The initial microchips were easy to hack, typically by scratching off the programming-voltage contact on the card, which rendered the phone unable to reduce the card's value after a call. But by the mid-to-late 1990s, highly secure technology aided the spread of chip phonecards worldwide. Remote memory systems Making a remote memory prepaid or calling card call requires the user to make two calls. It is necessary to dial an access telephone number to connect to the calling card system. There are several methods. One is via a toll-free number, with larger companies offering this internationally. Access through a local number has become increasingly popular in recent years. Toll-free calls are paid for by the recipient (the calling card company), which passes on the cost through higher call charges; total cost of a call to the user is often lower using a local number. When travelling through several local areas a toll-free service may be preferable. Once connected to the access number, the account is identified by keying in a PIN (the most popular method) or by swiping a card with embedded chip or magnetic stripe. After validation the balance remaining on the card may be announced, and the desired number may be keyed in. The available minutes may be announced, and the call is