A data terminal is connected to a telephone line for data transmission and reception. When a malfunction is detected in the data terminal, the data terminal is automatically disconnected from the telephone line and a telephone set connected to the telephone line. After a predetermined time interval, the telephone set is automatically disconnected from the telephone line and the data terminal re-connected to the telephone line.

A transaction execution system having a multiple account data base and a plurality of transaction terminals in communication with the host. The terminals each include a keyboard, a display, document handlng subsystems, a hardware control subsystem, a communication subsystem and a programmable control subsystem supervising the other subsystems. A user initiates a transaction request by inserting a card, which may have been issued by any of a plurality of cooperating card issuers or banks, into one of the terminals. The issuer identification number is read from the card, and used to search a table of card format and encryption key data. If the corresponding format and key data is located in the table, the terminal requests entry of a preassigned personal ID number through the keyboard. Verification data located on the card by format data from the table is encrypted in response to the key data from the table for comparison with the keyboard entered ID number. If the corresponding format and key data is not located in the table, the card data is sent to the host, which accesses a master table with the issuer identification number, and communicates back to the terminal the corresponding format and key data located in the master table. Once the terminal has checked for correspondence between encrypted verification data and the ID number, in response to format and key data from its own table or communicated from the host, additional transaction data is obtained via the keyboard. Upon command from the host, the host supplied format and key data is purged by the terminal at completion of the transaction, or else retained for future reference.

A credit status verification system and method that affords high flexibility for use by merchants and bankers has a high speed, high capacity, on-line, real time computer which stores data concerning the credit status of the bearer of a particular decimal number, usually a customer bank account number. A plurality of terminal units in stores and/or banks generate input messages in a binary coded digital signal form to be received by the computer, and the computer produces output messages in a binary coded digital signal form to be sent to the terminal units preferably over telephone lines. A polling unit at the computer is used to continuously interrogate the terminal units to see if they are operational and if they have any input messages ready and also recognize poll-type input messages. Address characters with the messages locate the terminals and identify the incoming messages. A converter is used at the computer to step down the speed and change codes for output messages while changing them to asynchronous and to step up the speed and change codes for input messages while changing them back to synchronous. Interface controllers for the terminal units facilitate one controller remote from the computer for a plurality of terminal units, distinguishes between poll-type and response-type messages, and identifies the terminal unit for receipt of the input messages by the computer.

A public access network operating in conjunction with existing telecommunication lines to permit a caller holding a machine-readable credit card to make calls from any local station included in the network without having to deposit coins and without human intervention. The network is constituted by a management and master control central linked to a group of satellites installed at different locations, such as airport terminals. At every installation, the satellite services a plurality of local telephone stations each provided with a standard telephone set, a card reader adapted to scan the caller's credit card to derive therefrom a digital signal identifying the card, its number and expiration date, this signal being applied to a local processor to determine whether the card is acceptable to the network. If the card is rejected, the call is terminated, and if accepted, the card data is then transferred from the local processor to a verifying processor at the satellite to test the card number against a stored table of invalid numbers. If the card passes this test the local processor is so advised, the processor then activating the telephone set to permit the caller to dial.

A public access network operating in conjunction with existing telecommunication lines to permit a caller holding a machine-readable credit card to make calls from any local station included in the network without having to deposit coins and without human intervention. The network is constituted by a master control central linked to a group of satellites installed at different locations, such as airport terminals. At every installation, the satellite acts as a hub for many local telephone stations each provided with a standard telephone set and a card reader adapted to scan the caller's credit card to derive therefrom a digital signal identifying the card, its number and expiration date. This signal from an originating local station is transmitted through the associated satellite to a verification processor at the central to test the card number against a stored table of invalid numbers and in other respects to determine the acceptability of the card. If the card passes this test the originating local station is so advised and the telephone set is then activated to permit the caller to dial.