Adapter circuitry for computers to support computer telephony

摘要

An external adapter circuitry is plugged into the printer port of a host computer to provide the utility of computer telephony for the host computer. The circuitry is housed in a compact box which is about the size of a common parallel port connector. The circuitry consists of a telephone line interface for receiving and sending signals from/to the telephone line; a printer port interface for sending data to and receiving data from the host computer; a couple of registers for latching signal-in and signal-out; a A/D converter for converting analog signals to digital signals; and a D/A converter for converting digitized signals to analog signals. More specially, the electricity of the entire circuitry is supplied from a signal-to-power converter which obtains voltages from the printer port. Therefore, the external adapter circuitry does not need a power line for external power supply.