Mastercard II provides Apple II+ and //e owners with a versatile, dual function interface. An asynchronous serial port conforming to RS232 standards is combined with an 8-bit parallel 'user port'. The serial port is intended for use in conjunction with communications software such as Data Highway and can be used to communicate bi-directionally with a variety of remote devices, including terminals, printers, nad other computers. All such devices may be connected either directly or via a modem to Mastercard II. A specifc use of the user port is with auto-dialling modems such as Nightingale.