Communication device employing a low impedance transformer

摘要

A communication interface circuit is connected to a tip terminal and a ring terminal establishing a call connection through a public switched telephone network to provide an interface between a modem and the public switched telephone network. The communication interface circuit includes a first capacitor, a transformer, and a first resistor. The first capacitor is serially connected to the tip terminal. The transformer has a primary coil connected to the first capacitor and a secondary coil connected to the modem. The transformer includes a low impedance to match an impedance between the modem and the public switched telephone network. The first resistor is serially connected to the primary coil of the transformer.