Patent ID: 6298124
Filing Date: 2001-10-02
Classification: H04M

Abstract:
A method for transmitting data signals on analog subscriber lines between a subscriber terminal equipment and a telephone exchange, Preferably during speech signal transmission of an existing telephone connection, comprising the steps of:providing a carrier signal generator in the telephone exchange;providing a data source in the telephone exchange;providing a modulator in the telephone exchange;modulating the data signals in a subscriber circuit and in the subscriber terminal equipment onto a signal with perodic characteristics serving as a carrier signal that has a frequency iying outside a speech band and that is already generated at least in the telephone exchange for some other use, the data signals delivered by the data source being modulated onto the carrier signal delivered by the carrier signal generator;filtering out modulation products falling in the speech signal range at a transmit side;superimposing the modulated carrier signal and the speech signal;filtering out the modulated carrier signal at a receive side;connecting a demodulator downstream of the filtering step;connecting a data evaluation circuit to the demodulator; andblocking the carrier signal frequency connected to the telephone terminal of the subscriber terminal equipment upstream with a filtering unit.