Cordless telephone-to-sound card interface adapter with hybrid transformer and control circuit

• US 20050003858A1
• Filed: 05/18/2004
• Published: 01/06/2005
• Est. Priority Date: 07/02/2003
• Status: Active Grant

• Current Assignee: NVG, Inc.
• Original Assignee: NVG, Inc.
• Inventors: Herrig, Hanz Werner, Rodriguez, Luis Ricardo
• Granted Patent: US 7,006,625 B2
• Time in Patent Office: Days
• US Class Current: 455/556.100
• CPC Class Codes: H04M 1/2535 adapted for voice communication over an Internet Protocol [IP] network Voice over Internet Protocol (VoIP) network equipment and services H04M7/006; implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP] H04L69/16
• CPC Class Codes: H04M 1/72502 with one base station connected to a single line

Abstract

A cordless telephone-to-sound card interface adapter provides a connection between any standard cordless telephone system and a sound card of a computer for PC-to-PC or PC-to-telephone voice communications over the Internet. The interface adapter includes a hybrid transformer circuit for interfacing a two-wire circuit of the cordless telephone and a four-wire circuit of the computer sound card. Consisting of passive components, this hybrid transformer circuit cancels out the voice echo that would otherwise exist due to mismatched impedances between the two media and/or from leakage of the signal being transmitted and received on the same pair of telephone lines. Preferably, a Universal Serial Bus (USB) interface is provided to supply a bias voltage to the cordless telephone system through the interface adapter. The interface adapter may also include interfaces for connecting with external computer speakers and microphone, and a control circuit for automatically switchably coupling the computer sound card to either the cordless telephone or the external speakers and microphone as appropriate.

Claims

1. A cordless telephone-to-sound card interface adapter for providing mobility to an end user during voice communications over the Internet, comprising:

a housing unit;

a hybrid transformer circuit carried in the housing unit;

the hybrid transformer circuit including;

a first hybrid transformer;

a second hybrid transformer coupled to the first hybrid transformer;

an impedance matching circuit coupled to the first and the second hybrid transformers;

a telephone jack coupled to the first and the second hybrid transformers and being configured to connect to a cordless telephone system with a telephone cord;

a speaker plug for coupling to the first hybrid transformer and being configured to connect to a speaker jack of a computer sound card; and

a microphone plug for coupling to the second hybrid transformer and being configured to connect to a microphone jack of the computer sound card.

2. The interface adapter of claim 1, further comprising:

a Universal Serial Bus (USB) interface for supplying a bias voltage to the cordless telephone system through the interface adapter.

3. The interface adapter of claim 1, further comprising:

a speaker jack being configured to connect with an external speaker;

a microphone jack being configured to connect with an external microphone;

a control circuit coupled to the hybrid transformer circuit;

the control circuit being operative to switchably connect the speaker plug and the microphone plug to the first and the second hybrid transformers, respectively, in response to detecting a telephone off-hook condition; and

the control circuit being operative to switchably connect the speaker plug and the microphone plug to the speaker jack and the microphone jack, respectively, in response to detecting a telephone on-hook condition.

4. The interface adapter of claim 1, further comprising:

a speaker jack being configured to connect with an external speaker;

a microphone jack being configured to connect with an external microphone;

a control circuit coupled to the hybrid transformer circuit;

the control circuit comprising;

a transistor switch;

a comparator having a first input coupled to the telephone jack, a second input coupled to a reference voltage, and an output coupled to an input of the transistor switch;

a first relay for switchably coupling the speaker plug between the speaker jack and the first hybrid transformer responsive to an output of the transistor switch; and

a second relay for switchably coupling the microphone plug between the microphone jack and the second hybrid transformer responsive to the output of the transistor switch.

5. The interface adapter of claim 1, wherein the hybrid transformer circuit consists of passive components.

6. The interface adapter of claim 1, wherein the impedance matching circuit comprises a resistor.

7. The interface adapter of claim 1, wherein the impedance matching circuit consists of a resistor.

8. The interface adapter of claim 1, further comprising:

the first hybrid transformer including a coil A which is inductively coupled with coils B and C formed along the same core; and

the second hybrid transformer including a coil F which is inductively coupled with coils D and E formed along the same core.

9. The interface adapter of claim 1, further comprising:

the first hybrid transformer including a coil A which is inductively coupled with coils B and C formed along the same core;

the second hybrid transformer including a coil F which is inductively coupled with coils D and E formed along the same core;

a first terminal of the coil C and a first terminal of the coil E coupled to the telephone jack;

a second terminal of the coil C coupled to a second terminal of the coil E;

first and second terminals of the coil A for coupling to the speaker plug;

first and second terminals of the coil F for coupling to the microphone plug;

a first terminal of the coil B coupled to a second terminal of the coil D;

a second terminal of the coil B and a first terminal of the coil D coupled to the impedance matching circuit.

10. The interface adapter of claim 1, further comprising:

first mutually-coupled coils A and C of the first hybrid transformer;

second mutually-coupled coils B and D of the first hybrid transformer which are formed along the same core as the first mutually-coupled coils A and C;

first mutually-coupled coils E and G of the second hybrid transformer; and

second mutually-coupled coils F and H of the second hybrid transformer which are formed along the same core as the first mutually-coupled coils E and G.

11. The interface adapter of claim 1, further comprising:

first mutually-coupled coils A and C of the first hybrid transformer;

second mutually-coupled coils B and D of the first hybrid transformer which are formed along the same core as the first mutually-coupled coils A and C;

first mutually-coupled coils E and G of the second hybrid transformer;

second mutually-coupled coils F and H of the second hybrid transformer which are formed along the same core as the first mutually-coupled coils E and G;

a first terminal of the coil D and a first terminal of the coil F coupled to the telephone jack;

a second terminal of the coil D coupled to a second terminal of the coil F;

a first terminal of the coil A and a first terminal of the coil B for coupling to the speaker plug;

a first terminal of the coil G and a first terminal of the coil H for coupling to the microphone plug;

a first terminal of the coil C coupled to a second terminal of the coil E;

a second terminal of the coil C and a first terminal of the coil E coupled to the impedance matching circuit.

12. A hybrid transformer circuit for a cordless telephone-to-sound card interface adapter, comprising:

a first hybrid transformer having a coil A which is inductively coupled with coils B and C formed along the same core;

a second hybrid transformer having a coil F which is inductively coupled with coils D and E formed along the same core;

an impedance matching circuit;

a first terminal of the coil C and a first terminal of the coil E for coupling to a cordless telephone system;

a second terminal of the coil C coupled to a second terminal of the coil E;

first and second terminals of the coil A for coupling to a speaker jack of a computer sound card;

first and second terminals of the coil F for coupling to a microphone jack of the computer sound card;

a first terminal of the coil B coupled to a second terminal of the coil D; and

a second terminal of the coil B and a first terminal of the coil D being coupled to the impedance matching circuit.

13. The hybrid transformer circuit of claim 12, further comprising:

a telephone jack coupled to the first terminals of the coils C and E and being configured to connect to the cordless telephone system with a telephone cord;

a speaker plug for coupling to the first and the second terminals of the coil A; and

a microphone plug for coupling to the first and the second terminals of the coil F.

14. The hybrid transformer circuit of claim 12, further comprising:

a Universal Serial Bus (USB) interface coupled to the hybrid transformer circuit for supplying a bias voltage to the cordless telephone system.

15. The hybrid transformer circuit of claim 12, further comprising:

a telephone jack coupled to the first terminals of the coils C and E and being configured to connect to the cordless telephone system with a telephone cord;

a speaker plug for coupling to the first and the second terminals of the coil A;

a microphone plug for coupling to the first and the second terminals of the coil F;

a speaker jack being configured to connect with an external speaker;

a microphone jack being configured to connect with an external microphone;

a control circuit being operative to switchably connect the speaker plug and the microphone plug to the first and the second terminals of the coils A and F, respectively, in response to detecting a telephone off-hook condition; and

the control circuit being operative to switchably connect the speaker plug and the microphone plug to the speaker jack and the microphone jack, respectively, in response to detecting a telephone on-hook condition.

16. The hybrid transformer circuit of claim 12, further comprising:

a telephone jack coupled to the first terminals of the coils C and E and being configured to connect to the cordless telephone system with a telephone cord;

a speaker plug for coupling to the first and the second terminals of the coil A;

a microphone plug for coupling to the first and the second terminals of the coil F;

a speaker jack for coupling to the first and the second terminals of the coil A and being configured to connect with an external speaker;

a speaker jack being configured to connect with an external speaker;

a microphone jack being configured to connect with an external microphone;

a control circuit coupled to the hybrid transformer circuit;

the control circuit comprising;

a transistor switch;

a comparator having a first input coupled to the telephone jack, a second input coupled to a reference voltage, and an output coupled to an input of the transistor switch;

a first relay for switchably coupling the speaker plug between the speaker jack and the first and the second terminals of the coil A responsive to an output of the transistor switch; and

a second relay for switchably coupling the microphone plug between the microphone jack and the first and the second terminals of the coil F responsive to the output of the transistor switch.

17. The hybrid transformer circuit of claim 12, wherein the hybrid transformer circuit consists of passive components and the impedance circuit comprises a resistor.

18. A telephone-to-sound card interface adapter, comprising:

a housing unit;

a hybrid transformer circuit carried in the housing unit;

the hybrid transformer circuit including;

a first hybrid transformer;

a second hybrid transformer being inductively coupled to the first hybrid transformer;

an impedance matching circuit coupled to the first and the second hybrid transformers;

a telephone jack coupled to the first and the second hybrid transformers and being configured to connect to a telephone system using a telephone cord;

a speaker plug for coupling to the first hybrid transformer and being configured to connect to a speaker jack of a sound card;

a microphone plug for coupling to the second hybrid transformer and being configured to connect to a microphone jack of the sound card;

a speaker jack being configured to connect with an external speaker;

a microphone jack being configured to connect with an external microphone;

a control circuit being operative to switchably connect the speaker plug and the microphone plug to the first and the second hybrid transformers, respectively, in response to detecting an off-hook condition of the telephone system; and

the control circuit being operative to switchably connect the speaker plug and the microphone plug to the speaker jack and the microphone jack, respectively, in response to detecting an on-hook condition of the telephone system.

19. The interface adapter of claim 18, further comprising:

a Universal Serial Bus (USB) interface for supplying a bias voltage to the telephone system through the interface adapter.

20. The interface adapter of claim 18, wherein the hybrid transformer circuit consists of passive components and the impedance matching circuit comprises a resistor.