Patent ID: 7907659
Filing Date: 2011-03-15
Classification: H04M

Abstract:
1. A multiple tone modem, comprising: a line interface circuit having a hybrid circuit with both one or more transmit transformers and one or more receive transformers to interface the multiple tone modem to a communication line, wherein the hybrid circuit comprises: a first transmit transformer with device side windings coupled to a line driver and with communication line side windings coupled to the communication line; a second transmit transformer with device side windings coupled to the line driver and with communication line side windings coupled to the communication line; a first receive transformer for a receive signal with device side windings coupled to a receiver and with communication line side windings coupled to the communication line; and an impedance component coupled to the communication line side windings of the receive transformer and the communication line side windings of the first transmit transformer, wherein the impedance component substantially matches an impedance value of the line to cancel the transmit signal from the receive signal.