WO2000035179A1

WO2000035179A1 - Computer-telephone-sound card interface method and apparatus

Info

Publication number: WO2000035179A1
Application number: PCT/US1999/029254
Authority: WO
Inventors: John A. Nix, Jr.
Original assignee: Go2Call.Com, Llc
Priority date: 1998-12-10
Filing date: 1999-12-10
Publication date: 2000-06-15
Also published as: AU2171800A

Abstract

A method and apparatus for a computer-telephone-sound card interface system (40) by which a general purpose personal computer is enabled to pass audio signals directly between a sound card (41) to a telephone handset (18). When the modem (10) has not seized the telephone line (14), audio signals are passed directly between the sound card (41) and the external speakers (30) and microphone (24). The interface system (40) automatically detects when the modem (10) seizes the telephone line (14), and passes audio signals between the sound card (41) and telephone handset (18) only when the handset (18) goes off hook. This interface system (40) facilitates personal computer functions such as Internet telephony over a regular phone or a cordless phone, without requiring the user to push buttons, switches, or disconnect and reconnect audio and telephone cables.

Description

Computer - Telephone - Sound Card Interface Method and Apparatus

Background of the Invention

The present invention relates generally to systems which exchange audio signals between a personal computer and an individual user. More particularly, the present invention relates to a method and apparatus for connecting a telephone handset to the personal computer's sound card.

One common and growing application for personal computers is voice communications over the Internet, or Internet telephony. In Internet telephony, the personal computer digitizes voice signals and exchanges the voice signals with another user connected to the Internet. The voice signals are generally input into the computer through an external microphone coupled to an internal sound card. Audio signals are output through a set of external speakers which are also coupled to the sound card .

Presently, several products which connect a telephone to a personal computer are available. One existing product is the "VoiceNet" by Columbia-Tel. The "Voice Net" connects a telephone to a personal computer sound card. When using this device, the telephone handset can be operated in one of two possible modes. In the first mode, the telephone is connected to the telephone company and operates as a regular telephone. In the second mode, the telephone is connected to the audio interface to the PC through the sound card. In order to switch back and forth between these two modes, the user must manually activate a push-button. To switch the audio from the personal computer speakers to the telephone earpiece, a second push-button must be activated.. For example, when an individual picks up the phone and wants privacy, the second pushbutton must be pushed to turn the speakers off.

Also, the "VoiceNet" does not have an input for an external microphone. Consequently, if an individual wants to sit in front of the PC and input voice through an external microphone, the user must manually unplug the microphone cable of the "VoiceNet" and plug in the external microphone cable to the sound card's microphone jack. This device, therefore, requires significant interaction between the user and the telephone. Furthermore, the device is not well-suited for use with a cordless phone.

Other products provide a telephone interface to the personal computer's sound card. The INTIOOCS by Riparius Ventures is a telephone handset with two 3.5 mm plugs to connect to the sound card instead of the standard RJ-11 connector common in North America. The primary shortcoming of the INTIOOCS is that it is corded, and will not allow the mobility to move about the room or house that a cordless phone allows. Also, the INTIOOCS does not automatically turn off the external speakers for privacy when the user is talking. For private conversations, the user must manually turn down the speakers. If the user wants to listen to the external speakers after using the INTIOOCS privately, the external speaker volume must then be increased again to be audible. Finally, the INTIOOCS does not provide the convenience of using the same telephone for both regular calls to the PSTN and internet calls, since the INTIOOCS interfaces only with the personal computer's sound card.

Many products such as the Internet Phone Jack by Quicknet connect a telephone directly to the computer through an expansion board m the PC. These boards duplicate many of the functions built into the sound card such as analog-to-digital conversion. Also, these boards require the user to open the PC. insert the card, and configure the operating system and software to properly communicate with the board. The cost for these boards is generally much higher than the cost for a simple external connector. These boards also do not directly control external speakers or microphones.

Therefore, although products for connecting a telephone to a personal computer to provide Internet telephony exist, they suffer from significant disadvantages. Existing devices generally require manual interaction between the user and the equipment in order to make the connection between the telephone and the personal computer. Because manual interaction is required, a user must physically sit in front of his or her computer to initiate an Internet telephone call. These devices, therefore, are not suited for uses with cordless telephones, which are increasingly common in American households. Furthermore, internet telephony often relies on the computer microphone and speakers to provide audio signals, these connections often provide poor quality audio signals. The microphone connected to a personal computer system, for example, is typically located at a distance from the speaker's mouth, and therefore generates poor quality sound. Moreover, the speakers are generally provided to broadcast sound across a room, and do not provide the pπvacy required for telephone conversations.

It is therefore an object of the invention to provide a device for providing Internet telephony through the handset of a standard or cordless telephone.

It is a further object of the invention to provide a signal converter for connecting a telephone handset to the sound card of a personal computer.

It is another object of the invention to provide a signal converter which automatically switches audio signals between an external microphone and external speakers connected to a personal computer and a telephone handset when the personal computer modem has seized the line and the handset of the telephone is lifted off of the hook.

It is a still further object of the invention to provide an Internet telephony system which is suitable for use with cordless telephones.

The present invention provides an effective solution to each of the shortcomings of the prior art by providing a system for automatically switching the audio signals from the external speakers and microphones of the personal computer to a telephone interface when the modem is in use and the telephone handset is lifted. When this condition is detected, the present invention automatically switches the personal computer's audio interface to the telephone handset, such that Internet telephony conversations can be conducted in the same way as telephone conversations conducted through a typical telephone connection to a telephone service provider. The circuitry to perform the detection and switching can be: incorporated in an external device; added to the sound card, motherboard, or other printed circuit board in a computer; otherwise installed internally in a computer; added to the telephone; or otherwise installed between a personal computer and a telephone.

In one preferred embodiment, the present invention comprises an interface box which is connected between a personal computer, a telephone, and an external microphone and external speakers. Externally, the interface device includes a plurality of connection points for connecting the interface box between a computer sound card, a computer modem, the telephone, the external microphone, and the external speakers. Internally, the interface box comprises an internal signal converter circuit board including a voltage detection function for monitoring voltage on the telephone line without interfering with normal telephone usage, a filtered power supply for the telephone handset, a system to detect when both the telephone handset is "off-hook" and the modem has seized the telephone line, and a system to switch between "normal through" operation of the signal converter wherein the sound cards signals are directly passed between the microphone and speakers only to "computer phone" operation wherein the sound card signals are directly passed to the telephone handset.

Brief Description of the Drawings

The invention, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which:

Figure 1 is a diagram showing how the present invention will interface with a personal computer, telephone, external speakers, external microphone, modem, and power.

Figure 2 is a flowchart showing the logic of the automatic switching in the invention. This diagram shows which actions cause the device to switch the routing of audio signals from the personal computer to the telephone.

Figure 3 is a complete electrical diagram outlining one implementation of a circuit with the features described.

Figure 4 is a complete electrical diagram outlining an alternative implementation of a circuit with the features described.

Figure 5 is a complete electrical diagram outlining an alternative implementation of a circuit with the features described.

Detailed Description of the Preferred Embodiments

Many personal computers sold during the past several years have come installed with an internal modem 10. As shown in FIG. 1, these modems 10 typically have two RJ- 11 female jacks - the first RJ-11 jack 12 leads to the telephone company's central office via a telephone line 14, and the second RJ-11 jack 16 connects to a telephone. Under "normal" conditions, when the modem 10 has not seized the telephone line 14, the telephone handset 18 is directly connected to the central office. When the telephone handset 18 goes off-hook, a dial tone can be detected. Although the telephone connection is described as a handset, it will be understood by those of ordinary skill in the art that any connection point to a telephone for connecting the audio signals, whether in the base, the handset, or other point on a telephone, could also be used. The connection point will be determined by the layout of the telephone

In order for many personal computers to connect to an external network such as the Internet, the modem 10 must seize the telephone lme 14 to place a call. When the modem 10 seizes the line 14, the modem's RJ-11 jack 16 connected to the telephone handset 18 is "dead", or disconnected from the telephone network. This prevents a person from interrupting the session the modem 10 established to log into the external network. A dial-up session can be easily broken by an individual picking up a different extension on the same telephone line.

In addition to the internal modem 10. most personal computers are equipped with an internal sound card or sound card functionality built directly onto the motherboard 41. The sound card 41 includes an input connector or microphone jack 22 to couple an external microphone to the personal computer and a speaker output connection 28 for connecting external speakers. The microphone jack 22 provides a port for inputting voice and other audio signals to an internet telephony connection, while the speakers provide a port for transmitting the audio sounds to the user.

The present invention provides a method and apparatus for automatically switching the audio input and output signals normally directed to a personal computer sound card to a regular or cordless telephone when the modem has seized the line and the telephone handset is off the hook. Referring now to FIG. 2. the method of the present invention generally comprises the steps of continually monitoring modem input lines to detect that a modem has seized the line, continually monitoring telephone input lines to detect that the telephone handset has been lifted, and. when both conditions are met, automatically switching the audio signals from the personal computer to the telephone. When the telephone is returned to an on-hook position, the audio signals are again switched to the external microphone and speakers, provided that the modem has not hung up the input telephone line. When the modem has hung up the telephone line, the telephone is automatically connected to the input telephone line to receive telephone calls as typically expected.

Referring again to FIG. 1, an interface device constructed in accordance with one preferred embodiment of the invention is shown at 40 The interface device 40 is coupled to the computer sound card 41, the computer modem 10, a telephone handset 18, an external microphone 24, and external speakers 30. Under "normal" conditions, when the modem 10 has not seized the telephone line 14, the interface device 40 couples the telephone handset 18 to the modem's RJ-11 jack 16 that is designated for the telephone handset. The signals from the sound card's "To Speaker" speaker output connection 28 are passed directly to the external speakers 30 and the input from the external microphone 24 is passed directly to the sound card's microphone jack 22. When the modem 10 has seized the input telephone line 14, and the telephone handset 18 is taken off hook, circuitry in the interface device 40 switches the audio signal input to the microphone jack 22 on the sound card 41 from the external microphone 24 to the telephone mouthpiece 26. The interface device 40 further switches the audio output signal from the speaker output connection 28 to the telephone earpiece 32, so that both input and output audio signals are directed through the telephone handset 18. While generally the connections to the audio signals are located on a sound card 41, it will be apparent to one of ordinary skill in the art that the audio signals could be connected through other internal or external boards in the personal computer.

Externally, the interface device 40 includes a plurality of connectors for connecting the interface device 40 between the computer sound card 41, the computer modem 10, a telephone handset 18, an external microphone 24, and external speakers 30. An audio output jack 11 and audio input jack 13 are provided to connect the interface device 40 to the computer's sound card "microphone in" jack 22 and speaker output jack 28, respectively. A microphone in jack 15 for attaching the microphone 24, and a speaker in jack 17 for attaching speakers 30 are also provided. Two RJ-11 connectors, a telephone jack 19 and modem jack 21 provide connection points for connecting the telephone handset 18 and modem 10, respectively. Finally, an input voltage connector 23 is provided to couple an external low level voltage, preferably 12 VDC, to the interface device 40. Preferably, the voltage is supplied by an external adapter 25 which converts a standard 120 VAC voltage supply to 12 VDC. Internally, the interface device 40 comprises an internal signal converter circuit board including a voltage detection function for monitoring voltage on the telephone line without interfering with normal telephone usage, a filtered power supply for the telephone handset, a system to detect when both the telephone handset is "off-hook" and the modem has seized the telephone line, and a system to switch between "normal through" operation of the signal converter wherein the sound cards signals are directly passed between the microphone and speakers only to "computer phone" operation wherein the sound card signals are directly passed to the telephone handset.

A circuit diagram that illustrates one implementation of the signal converter board is shown in FIG. 3. This implementation will be appreciated by those skilled in the art, and this particular implementation is described in detail below. Many other implementations are possible that can provide the same functionality.

As noted above, power is supplied to the signal converter board through an input voltage connector 23. When a voltage is applied to this connector, the LED 49 is activated, providing a signal that the interface device 40 is receiving operational power.

The input voltage from the modem 10 is rectified across a full- wave bridge rectifier 50 and divided across a voltage divider 52 comprising the resistors 51 and 53 for input into an op-amp 54. The op-amp 54 is configured to function as a comparator. Under "normal" conditions, when the modem 10 has not seized the telephone line 14 and the telephone handset 18 is not off-hook, the voltage between the two wires of the modem input 21 is approximately 50 volts. The invention utilizes diodes 59 to rectify the voltage, in case the polarity on the two telephone lines 21 has been reversed. The op-amp 54 compares the input voltage to ground, and if the voltage is higher than ground, the op-amp 54 will output a signal of approximately 1.5 volts. When the modem 10 seizes the telephone line 14, the voltage on the line connected to the modem's "To Phone" jack 16 will fall close to 0 volts. The op-amp 54 functioning as a comparator senses the voltage fall, and outputs a "high" voltage of approximately 8 volts. Although a full-wave rectifier is shown, it will be apparent to those of ordinary skill in the art that other types of circuits, such as differential op-amps can also be used to determine an absolute input voltage. Furthermore, although a full wave rectifier is shown, other types of rectifier circuits may also be employed.

The voltage output from the op-amp 54 will only be set high when the voltage on the line 21 connected to the modem's "To Phone" jack falls close to 0 volts. This allows multiple other telephone handsets on the same telephone line to be "off hook" and the op-amp 54 will still output a low voltage. With one telephone handset off hook, the voltage on line 21 typically falls from 50 volts to 9 volts. With a second handset off hook on , the voltage on line would typically fall from about 9 volts to about 6 volts. Through setting the reference voltage on the non-inverting input on op-amp 54 to ground, multiple extensions can be off-hook without the output of op-amp 54 being set high.

The "high" voltage output from the op-amp 54 has two functions. First, the "high" voltage provides a small current which in turn is amplified through a transistor 60 to provide current to activate a relay 62. The relay 62 connects the telephone handset 18 to a filtered power supply 64 preferably of substantially 9 volts dc, and current from the relay 62 passes through a light emitting diode (LED) 66 or other indicator device to indicate that the modem 10 has seized the telephone line 14. Second, the "high" voltage provides a small current which is amplified through a transistor 68 to control a second high- voltage transistor 70. The high voltage transistor 70 is preferably a NTE 194, manufactured by NTE Electronics, although other high voltage transistors may also be used. Furthermore, although a relay is shown, it will be apparent to one of ordinary skill in the art that other remote switching devices, analog switches, or other circuit elements could be used instead of a relay. Additionally, although a 9 volt power supply is specified, other low level signals suitable for use with op-amps and transistor logic could also be used.

Without this base current, the transistor 70 is normally off, and it prevents the flow of current through the transformer 72. For example, when the telephone receives a ringing signal of approximately 100 volts AC, the high- voltage transistor 70 prevents current from flowing through the circuit or transformer 72. The 100 volt ringing signal must be carefully isolated from the microphone jack 22 and speaker jack 28 connected to the personal computer. When the high-voltage transistor is off, almost all of the 100 volt ringing signal is prevented from passing through the transformer. When the modem has not seized the telephony line, a typical 100 V AC signal will result in no more than 50 mV AC signal on either microphone jack 22 or speaker jack 28.

Once the transistor 70 is conducting, no current will flow through the transformer 72 until the telephone handset 18 is off-hook. When the telephone handset 18 is lifted, the current from the filtered 9 volt power supply 64 can pass through the telephone handset 18, transformer 72, and the resistor 74. In this particular embodiment, the resistor 74 is selected to be substantially 150 ohms, but resistors of different values may also be used. Since the telephone handset 18 has been lifted and the computer has already seized the telephone line 14 to log into the network, this means the user must want to use the telephone as the audio interface with the PC. The user may want to use the telephone as the audio interface to conduct Internet telephony.

Although the circuitry as shown switches the telephone automatically, there may be some cases in which users may want to disable this feature It will be apparent to those of ordinary skill in the art that any number of switching devices could be used to disable the automatic switching.

Lifting the handset when the modem has seized the telephone line will result in a voltage across the resistor 74 Current generated by this voltage is passed to the base of two different transistors, transistor 78 and transistor 80, through the resistor 76. Current through the resistor 76 activates the transistor 78 controlling a second single pole double throw relay 82. and also activating the indicator LED 73. This relay 82 in turn controls the passing of audio signals between the personal computer and the external microphone 24 and speakers 18. The relay 82 is "normally closed", and under the normally closed position the ground for the external speaker 30 and microphone 24 is connected to the ground of the personal computer. When the relay 82 is activated by the telephone handset 18 going off-hook, the ground of the personal computer is instead connected to the ground of the secondary side of the transformer 72. Consequently, audio signals can be passed between the telephone handset 18 and the personal computer's sound card 41.

As noted above, the voltage across the resistor 74 also passes current to the base of the transistor 80. activating this transistor and providing a path to ground for selectively activating the LED 75. The op-amp 84 activates the transistor 86 which in turn activates the LED 75 to indicate when signals are being passed between the sound card 41 and the telephone handset 18.

The embodiment shown in FIG. 3 is configured for use with stereo speakers connected to a sound card with mono cables. In this configuration, therefore, the speakers would provide mono sound. Alternatively, as is shown in FIG. 4, the present invention can be configured for use with external stereo sounds. In this case, the relay 82 is a double pole double throw relay to separately switch the right and left channels of the external speakers.

The invention can also be configured for use with both dynamic and condenser microphones. Condenser microphones require external power, which is generally provided by the tip and ring lines on the cable from the sound card's microphone. As is shown in FIG. 3, therefore, when the telephone is connected to the personal computer, audio signals are transmitted through the tip and ring of the cable. FIG. 5 provides an alternative embodiment for use with a dynamic microphone. Dynamic microphones do not require external power, and audio signals are instead passed through the tip and sleeve of the cable. It will be apparent to those of skill in the art that the present invention can be configured to support all combinations of mono and stereo speakers, dynamic or condenser microphones, and stereo or mono cables.

Although the present invention has been shown as an external interface device 40 coupled externally between a personal computer and a telephone, it will be apparent to one of ordinary skill in the art that the invention could be embodied on a printed circuit board internal to the computer, or that any required circuitry could be added directly to a sound board, a mother board or other internal printed circuit board. Furthermore, the required circuitry could be added to a specialized telephone.

While preferred embodiments of the invention have been shown and described, it will be clear to those skilled in the art that various changes and modifications can be made without departing from the invention in its broader aspects as set forth in the claims provided hereinafter.

Claims

We claim:

1. A method for automatically switching audio signals between a computer and a

telephone, the method comprising:

detecting an off-hook condition for a telephone;

detecting that a modem has seized a telephone line; and

automatically switching the audio signals from the computer to the telephone when

the off-hook condition is detected and the modem has seized the telephone line.

2. The method as defined in claim 1. further comprising the step of comparing the

voltage on the telephone line to a predetermined value to detect that the modem has seized

the line.

3. The method as defined in claim 1. further comprising the step of switching the

audio signals from an external speaker and an external microphone to a telephone

handset.

4. The method as defined in claim 1, further comprising the step of coupling the

telephone to the telephone line when the modem has not seized the telephone line.

5. A switching apparatus for automatically switching audio signals between a

computer and a telephone, the switching apparatus comprising:

a modem detection circuit responsive to a modem seizing a telephone line to

produce a modem active signal; a telephone off-hook circuit responsive to a telephone being taken off hook to

produce a telephone active signal;

a switching circuit activated by the modem active signal and the telephone active

signal, the switching circuit configured to route audio signals from a computer sound card

to the telephone when the modem active signal and the telephone active signals are

received.

6. The switching apparatus as defined in claim 5, wherein the circuit responsive to

the modem seizing the telephone line is a voltage comparator.

7. The switching apparatus as defined in claim 6, wherein the voltage comparator is

activated when the voltage on an input telephone line is substantially ground.

8. The switching apparatus as defined in claim 5, wherein the modem active signal

activates the telephone detect circuit.

9. The switching apparatus as defined in claim 5, wherein the telephone detect circuit

is responsive to a voltage supplied by the modem detect circuit.

10. The switching apparatus as defined in claim 5, further comprising a switch to

disable the automatic switching.

1 1. The switching apparatus as defined in claim 5, wherein the switching circuit is

adapted to couple the telephone handset to the telephone line when the modem has

dropped the telephone line.

12. The switching apparatus as defined in claim 5, wherein the switching circuit

comprises a mother board in a computer.

13. An interface device configured to couple a telephone to an Internet connection for

use in Internet telephony, the interface device comprising:

a plurality of connectors, one said connector to couple a computer to the interface

device and another said connector to couple a telephone to the interface device;

a switching circuit configured to receive a modem active signal and a telephone

active signal and to switch audio signals from a computer sound card to a telephone when

the modem has seized a telephone line and the telephone is off hook.

14. The interface as defined in claim 13, further comprising a computer sound card

connector.

15. The interface as defined in claim 13, further comprising an external microphone

connector.

16. The interface as defined in claim 13, further comprising an external speaker

connector.

17 A method for using a voltage on a telephone line to automatically switch audio

signals between a computer sound card and a telephone, the method comprising the

following steps:

monitoring a voltage across a telephone mput line to determine when a modem has

seized the line;

providing a voltage to a telephone when the modem has seized the line;

monitoring the current through the telephone to determine when the telephone is

off-hook;

the computer has seized the line and the telephone is off-hook.

18. The method as defined in claim 17 further comprising the step of switching the

audio signals directly to the telephone when the modem has not seized the line.

19. The method as defined in claim 17, further comprising the step of switching an

audio input signal from an external microphone coupled to the computer to a mouthpiece

of the telephone.

20. The method as defined in claim 17, further comprising the step of switching an

audio output signal from an external speaker system coupled to the computer to an

earpiece of the telephone.

21. An interface for automatically switching the audio signals between a computer and

a telephone for Internet telephony, the interface comprising: a connection point for a telephone:

a connection point for a computer sound card;

a connection point for an external speaker system;

a connection point for an external microphone;

a connection point for a modem; and

a switching circuit, wherein the switching circuit is configured to:

route the incoming telephone line to the telephone when the modem has not

seized the line;

route audio signals to the external speaker and external microphone when

the modem has seized the line and the telephone is on-hook; and

route the audio signals to the telephone when the modem has seized the line

and the telephone is off-hook.

22. The apparatus as defined in claim 21, wherein the interface is a separate

component coupled between a telephone system and a computer system.

23. The apparatus as defined in claim 21, wherein the interface is built into a computer

case.

24. The apparatus as defined in claim 21, wherein a comparator in the switching

circuit provides a modem active signal when a voltage across the input telephone line

reaches a predetermined threshold value.

25. The apparatus as defined in claim 21, wherein the switching circuit supplies a

voltage to the telephone when the modem active signal is received.

26. The apparatus as defined in claim 21, wherein the switching circuit comprises at

least one relay for switching the audio signals between the telephone and the external

speaker and external microphone.

27. A method for providing Internet telephony through a telephone, the method

comprising the following steps:

establishing an Internet connection to a modem coupled to an input

communications line;

detecting that the modem has seized the communications line;

detecting that a telephone is off-hook;

the modem has seized the line and the telephone is off-hook to permit Internet telephony

through the telephone.

28. The method as defined in claim 27, further comprising the step of coupling the

telephone to the communications line when the modem has not seized the

communications line.

29. The method as defined in claim 27, further comprising the step of coupling an

interface box including a switching circuit between the telephone, the modem, and the

computer.

30. The method as defined in claim 29, wherein the interface box is coupled to existing

connectors on the telephone, the computer, and the modem.