Abstract: A telephony device such as a digital telephone or personal computer attaches to phone lines and automatically determines both the type of switch to which is connected, and the type of line card in the switch providing that connection. In addition, device functions and data types supported by the switch and line card are automatically determined, providing a fully automatically configurable device. Programming in the device monitors polling messages provided by the switch and line card having different formats to make the determination. The devices switch between two different flow control types supported by the different line cards, while listening for the polling messages. If a message is not received while using a first flow control type, the second is used. The capability of channel, voice or data, is also automatically determined once the switch type is known.