US 6,137,880 A · Passive splitter filter for digital subscriber line voice communication for complex impedance terminations

Abstract

A dual-mode filter network for an Asymmetric Digital Subscriber Line (ADSL) has a first frequency response when the Plain Old Telephone Service (POTS) telephone is on-hook and has a second frequency response when the POTS telephone is off-hook. A detector is used to determine the on-hook/off-hook status. The dual-mode filter network may be situated at the central unit and connected to a Public Switched Telephone Network (PSTN) while the detector at the remote unit connected between the POTS low pass filter and the POTS telephone. In such case, the detector outputs a signal which is transmitter via the twisted pair on an overhead channel. Alternatively, the dual-mode filter and the detector may be co-located at either the central unit or at the remote unit. Regardless of where it, or the detector are located, the dual-mode filter network has at least different combinations of components which are activated, depending on the on-hook/off-hook status of the POTS phone. In addition, a single-mode filter instead of the dual-mode filter can be used at the remote unit.

Claims20

Dependent claims

A filter comprising:

a first inductor having first and second coils, each of said coils having a first and a second terminal;
first and second resistors connected in series between the first and second terminals of said first coil;
a first capacitor connected in parallel with the first resistor, said first capacitor connected between one of the terminals of said first coil and a first node defined between said first and second resistors;
third and fourth resistors connected in series between the first and second terminals of said second coil;
a second capacitor connected in parallel with the third resistor, said second capacitor connected between one of the terminals of said second coil and a second node defined between said third and fourth resistors, wherein said first terminals of said first and second coils define a first port of said filter, and said second terminals of said first and second coils define a second port of said filter;
and
a third capacitor connected in parallel with said first port.

4 more elements

An asymmetric digital subscriber line (ADSL) system connecting a public switched telephone network (PSTN) to a plain old telephone system (POTS) switchable between an on-hook mode and an off-hook mode, said ADSL system comprising:

a central unit comprising a first filter having a first connection to said PSTN;
a remote unit comprising a second filter having a first connection to said POTS;
and
a transmission line connecting said first and second filters, wherein
said second filter comprises:
a first inductor having first and second coils, each of said coils having a first and a second terminal;
first and second resistors connected in series between the first and second terminals of said first coil,
a first capacitor connected in parallel with the first resistor, said first capacitor connected between one of the terminals of said first coil and a first node defined between said first and second resistors;
third and fourth resistors connected in series between the first and second terminals of said second coil;
a second capacitor connected in parallel with the third resistor, said second capacitor connected between one of the terminals of said second coil and a second node defined between said third and fourth resistors, wherein said first terminals of said first and second coils define a first port of said second filter, and said second terminals of said first and second coils define a second port of said second filter;
and
a third capacitor connected in parallel with said first port.

9 more elements

Dependencies are inferred from the claim text.

Passive splitter filter for digital subscriber line voice communication for complex impedance terminations

Life of this patent

Passive splitter filter for digital subscriber line voice communication for complex impedance terminations

Life of this patent

Abstract

Claims20