Patent ID: 6879687

Claim:
An apparatus for sending a ringing signal to notify a called terminal of the presence of an incoming call addressed the, comprising: ringing voltage generating means for generating a ringing voltage; ringing signal sending means for sending out a ringing signal over a subscriber line by outputting the ringing voltage with a predetermined duty cycle of a ringing period and a silent period; data transfer means for performing a data transfer to the called terminal over the subscriber line during one of the silent periods; feed impedance selection means working in conjunction with one or more switches to select a low-impedance feed voltage in the one of the silent periods during which the data transfer is performed, and selecting the a high-impedance feed voltage in the other silent periods during which no data transfer is performed; and feed impedance setting means for providing the high-impedance feed voltage to the subscriber line when said feed impedance selection means selects feeding of the high-impedance feed voltage, wherein the high-impedance feed voltage is realized by inserting a predetermined resistance on the subscriber line in series with a subscriber line circuit (SLIC) that drives the subscriber line, while the low-impedance feed voltage is provided by removing the predetermined resistance from the subscriber line.