Phonecard

A telephone card, calling card or phonecard for short, is a credit card size plastic or paper card, used to pay for telephone services (often international or long distance calling). It is not necessary to have the physical card except with a stored-value system; knowledge of the access telephone number to dial and the PIN is sufficient. Standard cards which can be purchased and used without any sort of account facility give a fixed amount of credit and are discarded when used up; rechargeable cards can be topped up, or collect payment in arrears. The system for payment and the way in which the card is used to place a telephone call vary from card to card.

Calling cards usually come equipped with PIN for user protection and security. Most companies require user to enter the PIN before granting access to the calling card’s funds. PINs often are printed on a piece of paper found inside the calling card’s packaging. Once the users makes their first call, some companies offer the option of eliminating the PIN altogether to speed up the calling process. Companies that sell virtual calling cards online typically PIN via email.

A stored-value phonecard contains the balance available on the card. This balance can be read by a public payphone machine when the card is inserted into the payphone's card reader. This is superficially similar to a bank automated teller machine, but a stored-value card is more closely analogous to a change purse. While ATMs (as well as the remote memory systems discussed below) use the card merely to identify the associated account and record changes in a central database, stored-value systems make a physical alteration to the card to reflect the new balance after a call. Used primarily for payphones, stored-value systems avoid the time lag and expense of communication with a central database, which would have been prohibitive before the 1990s. There are several ways in which the value can be encoded on the card.

The earliest system used a magnetic stripe as information carrier, similar to the technology of ATMs and key cards. The first magnetic strip phonecard, manufactured by SIDA, was issued in 1976 in Italy.

...
Wikipedia