Method and apparatus for generating a ringing signal

In generating a ringing signal of predetermined frequency and shape between the A- and B-wires to a subscriber's station in a telephone network, the ringing signal is directly injected in or superposed on the DC-levels of the wires. A voltage difference converting device converts any voltage difference between the A- and B-wires into a first current. A signal generating device generates a first voltage of the frequency and shape of the ringing signal to be generated, and a signal converting device then converts the first voltage into a second current. In a summation node the first current is subtracted from the second current to obtain a third current and this current is converted by passing it through a resistor to a second voltage. The second voltage is buffered and is again converted to a fourth current by applying the voltage to resistor. This fourth current is amplified by current amplifiers circuits comprising operational amplifiers, and is then supplied to the A-wire and drawn from the B-wire.