WO2000072568A1

WO2000072568A1 - Computer - telephone interface method and apparatus

Info

Publication number: WO2000072568A1
Application number: PCT/US2000/014006
Authority: WO
Inventors: John A. Nix, Jr.; Laurence A. Spear
Original assignee: Go2Call.Com, Inc
Priority date: 1999-05-21
Filing date: 2000-05-19
Publication date: 2000-11-30
Also published as: WO2000072568A9; AU5036300A

Abstract

A method and apparatus for a computer-telephone interface system by which a general purpose personal computer is enabled to pass audio signals directly between a sound card to a telephone handset. Under 'normal' operation (306), the telephone handset is connected directly to the telephone network, allowing normal telephone operation such as ringing or dial tone when the handset is lifted. The personal computer's audio signals are passed directly between the sound card and the external speakers and microphones. Once the handset is lifted (300), and a specified key on the touch-tone pad is the first key pressed (302), the interface system switches to 'computer phone' mode (304). The interface system disconnects the telephone from the telephone network, disconnets the personal computer's microphone and speakers, powers the telepone, and passes audio signals between the sound card and telephone handset. After the handset is returned to on-hook (308), the interface system, returns to 'normal' operation (306).

Description

Computer - Telephone 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 sound ports of a computing device.

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 either directly connected to the Internet or indirectly connected to the Internet through a gateway. 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. The microphone and speaker connections associated with personal computers, however, are often not satisfactory for use with Internet telephony. Particularly, the microphone and speaker connections to personal computers do not provide the privacy or the clarity of audio signals associated with traditional telephone systems.

Presently, several products which seek to correct these deficiencies by connecting 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 traditional telephone. In the second mode, the telephone is connected to an audio interface on the sound card of a personal computer, and is used for Internet telephony. In order to switch voice input connections from a microphone coupled to the personal computer to a telephone handset, the user must manually activate a push-button on the "VoiceNet". To switch the audio from the personal computer speakers to the telephone earpiece, a second push-button must be activated. Therefore, two pushbuttons must be activated to give a user the privacy normally associated with telephone communications. Activating multiple publications is a cumbersome procedure when attempting to place a phone call. Furthermore, 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 disconnect the microphone cable of the "VoiceNet" and connect the external microphone cable to the sound card's microphone jack. This device, therefore, requires significant interaction between the user and the telephone to provide communication devices suitable for both telephone and computer applications.

Another existing product which couples a telephone handset to a personal computer is the INT100CS by Riparius Ventures. The LNT100CS is a telephone handset with two 3.5 mm plugs which connect to the sound card of a personal computer. The telephone handset must be connected to the sound card, therefore, when Internet telephony is required, and disconnected and replaced with speakers and a microphone when standard personal computer operation is required. Again, this system requires a significant amount of setup to switch between applications. Furthermore, since the telephone handset is designed specifically for use with the sound card, it cannot be used in traditional telephone communications. Therefore, multiple telephone devices are required to provide both Internet and traditional telephone communications.

Many products such as the "Internet Phone Jack" by Quicknet connect a telephone directly to the computer through an expansion board in the PC. To install these boards, the user must open the PC, insert the card, and configure the operating system and software to properly communicate with the board. These devices, therefore also require a great deal of setup time. Furthermore, these boards are expensive and often duplicate many of the functions built into the sound. Therefore, they add significantly to the cost of a computer system without adding significant functionality.

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 often must physically sit in front of his or her computer to initiate an Internet telephone call. These devices, furthermore, are not suited for uses with cordless telephones, which are increasingly common in American households. Additionally, many of these devices require expensive and duplicative equipment which do not increase the functionality of the computer.

There exists a need, therefore, for a method and apparatus which provides a means for selectively switching the audio signals from a computer sound card, or other internal device, to a telephone handset when a user wishes to use Internet telephony. Preferably, such a device could be easily activated, without requiring significant reconnections by the user or activation of external devices. Furthermore, the device would employ available circuitry so as to not require the addition of expensive duplicative hardware.

It is therefore an object of the invention to provide a device which enables Internet telephony through the handset of a telephone.

It is further an object of the present invention to provide a signal converter for detecting an audio input signal and switching the audio ports of a personal computer between the computer and the telephone.

It is another object of the invention to provide a method and apparatus for selectively switching the audio ports of a computer between a speaker and microphone and a telephone handset.

It is still another object of the invention to provide an interface device which disconnects a telephone handset from the telephone network when a special audio signal is provided by the telephone handset, and reconnects the telephone handset to the telephone network when the telephone is returned on-hook.

It is another object of the invention to provide an interface device which switches audio signals from the speakers and microphone of a personal computer to a telephone handset when a special audio signal is provided by the telephone handset

The present invention provides an effective solution to each of the shortcomings of the prior art by providing a method and apparatus for automatically switching the audio signals from the speakers and microphone of a computing device to a telephone interface when the user lifts the handset and provides a predetermined signal. When this condition is detected, the present invention switches the personal computer's audio interface to the telephone handset, such that Internet telephony conversations can be conducted in the same way that telephone conversations are conducted through a typical telephone connection to a telephone service provider. Also, the telephone is disconnected from the telephone network. Generally, the apparatus of the present invention comprises an interface circuit which switches both input and output audio signals between the audio connections of a computer (on the motherboard, sound card, or other device) and a telephone handset. The switching circuitry allows for two modes of operation. In the first mode ("normal mode"), the telephone handset is coupled to a telephone network to provide traditional telephone communications. The computer audio input is coupled to a microphone or similar device, and the audio output is coupled to speakers. In the second mode ("computer phone mode"), the telephone handset is disconnected from the telephone network and coupled instead to the audio input and audio output ports of the computer. This connection allows a telephone user to use the telephone handset to communicate over a data network coupled to the computer rather than through the telephone network. Preferably, the switch is activated when the user activates a given key or sequence of keys on the telephone keyboard. However, any type of audio signal, voice signals, specialized input keys, or other switching signals could also be used.

In one embodiment, the present invention comprises an interface coupled between various computer and telephone components such as a telephone network, telephone handset, computer sound card, external speakers and microphones, and other devices. In alternate embodiments, the interface is coupled inside the case of a personal computer. Furthermore, it will be apparent to one of ordinary skill in the art that the circuitry to perform the described function could also be added to existing circuit boards in a personal or general purpose computer.

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 flowchart showing the logic of the 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 and disconnect the phone from the telephone network. Figure 2 is a diagram showing the connections between one embodiment of the present invention and a personal computer, telephone, external speakers, external microphone, telephone network, and power.

Figure 3 is an operational block diagram of the interface of FIG. 2.

Figure 4 is an electrical diagram showing one implementation of a circuit used in the interface of FIG. 2.

Figure 5 is an electrical diagram outlining one implementation of a logic circuit to detect when the user wishes to switch from the mode in which the telephone is connected to a telephone network to a second mode m which the telephone is connected directly to the personal computer

Figure 6 is a diagram of a second embodiment of the present invention wherein an interface is placed inside a personal computer.

Figure 7 is an electrical diagram showing one implementation of a circuit used m the interface of FIG. 6.

Figure 8 is a diagram of a third embodiment of the present invention, wherein the present invention is placed inside a personal computer or general purpose computing device with an internal speaker and microphone

Figure 9 is an electrical diagram showing one implementation of a circuit used in the interface of FIG. 8.

Figure 10 is a truth table outlining one implementation of the logic circuit shown in FIG. 5.

Detailed Description of the Preferred Embodiments

The present invention provides a method and apparatus for switching the audio input and output signals normally directed to the microphone and speakers connected to the sound card of a personal computer to a telephone when the user lifts the handset and provides a predetermined signal, preferably by pressing a special key or sequence of keys on the telephone keyboard.

Referring now to the Figures, and more particularly to FIG. 1, a flow chart showing the preferred method of implementing the present invention is shown. The method generally comprises the steps of continually monitoring signals from a telephone handset to detect when the handset has been lifted (step 300), monitoring input signals to determine whether a specific key or combination of keys has been pressed (Step 302), and switching the audio signals (Step 304) when the handset is lifted and the predetermined signal is detected. Under the "normal" configuration (Step 306), the microphone signals are automatically routed to a microphone jack on a personal computer, the audio output from the personal computer is automatically routed to external speakers, and the telephone is directly connected with the telephone network. When the handset is lifted and a special key (preferably the "#" key) is the first key dialed, the present invention automatically disconnects the telephone handset from the telephone network, provides power to the telephone handset, switches the audio signals from the personal computer to the telephone, and disconnects the external microphone and speakers from the personal computer (Step 304). When the telephone is returned to an on-hook position (Step 308), the audio signals from the personal computer are again switched to the external microphone and speakers and the telephone is automatically connected to the telephone network. The telephone can now receive telephone calls and the user will hear a dial-tone upon lifting the telephone off-hook, as typically expected.

Although the special key has been described as the "#" key, it will be apparent to those skilled in the art that other special keys or sequences of keys on the standard touch- tone key pad could also be used. The "#" key is preferred in the present invention, since several telephone features such as enabling or disabling call forwarding are activated by first hitting the "*" key. Also, number keys are generally pressed first when the user wishes to dial a telephone number. Furthermore, it will also be apparent to those skilled in the art that a voice command, or other audio input, could be used to switch the audio signals from the microphone and speakers to the telephone handset. Other types of signals, such as specialized switch inputs, could also be used.

It will be further apparent to those skilled in the art that the "normal" mode of operation could be the state where the telephone is connected to the sound card of the personal computer for use as a "computer phone." Upon providing the predetermined signal, the present invention would switch to the second state, where the telephone is connected to the telephone network and the speaker and microphone are connected to the sound card. Referring now to FIG. 2. an interface device constructed in accordance with one preferred embodiment of the invention is shown at 17 The interface device 17 is coupled to the computer sound card or audio section of the motherboard 14, a telephone 11, the telephone network 12, an external microphone 18, and external speakers 19. Under "normal" conditions (as defined above), the interface device 17 connects the telephone

11 directly to the telephone network 12. In this "normal" configuration, the signals from the sound card's "To Speaker" output connection 16 are passed directly to the external speakers 19, and the input from the external microphone 18 are passed directly to the sound card's 14 "To Microphone" connection 15. When "computer phone" mode is required, the telephone handset 11 is taken off-hook and the "#" key is the first key dialed, circuitry in the interface device 17, as will be described more fully below, disconnects the telephone handset 11 from the telephone network 12, switches the audio signal input to the microphone jack 15 on the sound card 14 from the external microphone 18 to the telephone mouthpiece 20. The interface device 17 further switches the audio output signal from the speaker output connection 16 to the telephone earpiece 21, so that both input and output audio signals are directed through the telephone handset 11. While generally the connections to the audio signals are located on a sound card 14, 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 17 includes a plurality of connectors for connecting the interface device 17 between the computer sound card or audio section of the motherboard 14, a telephone 11, the telephone network 12, an external microphone 18, and external speakers 19. An audio output jack 22 and audio input jack 23 are provided to connect the interface device 17 to the computer's sound card "microphone in" jack 15 and speaker output jack 16, respectively. A microphone in jack 24 for attaching the microphone 18, and a speaker in jack 25 for attaching speakers 19 are also provided. Two RJ-11 connectors, a telephone jack 26 and a telephone network jack 13 provide connection points for connecting the telephone handset 11 and the telephone network 12, respectively. Finally, an input voltage connector 27 is provided to couple an external low level voltage, preferably 12 VDC, to the interface device 17. Preferably, the voltage is supplied by an external adapter 28, which converts a standard 120 VAC voltage supply to

12 VDC. The computer further includes a modem or network adapter 9 that can be connected to an external data network 10. The network adapter 9 can be any of a number of connections which provides a communication link between the personal computer and external devices. Typically, the network adapter 9 is a dial-up modem, ethernet, DSL, cable modem, token ring, or Universal Serial Bus (USB), and the data network 10 is a local area network (LAN) or wide area network (WAN) such as the Internet. However, the data network 10 can also be any of a number of types of wireless networks, including cellular phone networks, satellite links, or other types of wireless cornmunications networks. The data network 10 provides the communications link between the telephone 11 and external users when in the "computer telephone" mode.

Internally, the interface device 17 includes an internal signal converter circuit board 30. Referring now to FIG. 3, a simplified block diagram showing the operation of the internal signal converter circuit board 30 is shown. Generally, the signal converter board 30 comprises a voltage detection function 310 for monitoring voltage on the telephone line without interfering with normal telephone usage and for determining when the telephone handset is "off-hook", a switch detect system 312 to detect when the input audio signal (or other type of input signal) matches a predetermined switching signal, preferably indicated when the first key dialed is the "#" key, and a switching system 314 to switch the audio signals when the telephone 11 is determined to be off hook by the voltage detection function 310 and the switch date of system 312 determines that the user has requested that the switch be activated. When activated, the switching system 314 preferably switches the audio signals from "normal" operation of the interface device 17, wherein the audio signals are passed directly between the personal computer's audio connections and the microphone and speakers only, to "computer phone" operation, wherein the audio signals are passed directly between the personal computer's audio connections and the telephone handset, and the external microphone and speakers are disconnected. Although a relay-based switching system is shown, it will be understood that the switching system shown is for illustrative purposes only, and is not meant to show actual circuitry. It will be apparent to those of ordinary skill in the art that any number of different types of switching circuits could be employed. Furterhmore, while the "normal" condition has been described as coupling the speaker and microphone to the sound card, it will be apparent to those of ordinary skill in the art that operation of the system could be converted such that "normal" mode of operation could be the state where the telephone is disconnected from the telephone network, and the audio signals are routed between the telephone and PC. Upon providing a predetermined audio signal, the present invention would then switch the audio signals to the second state, where the telephone is connected to the telephone network.

Additionally, although the predetermined audio signal has been described as the "#" key, it will be apparent to those of ordinary skill in the art that other special keys or sequences of keys on the standard touch-tone key pad could also be used. Furthermore, a voice command, other audio signal or other external switching devices could also be used to switch the audio signals.

A circuit diagram that illustrates one implementation of the signal converter board 30 is shown in Figure 4. It will be appreciated by those skilled in the art, that although a preferred implementation is shown, many other implementations that provide the same functionality are possible.

As noted above, power is supplied to the signal converter board 30 through an input voltage connector 27 (FIG. 2). When a voltage is applied to this connector, the LED 31 is activated, providing a signal indicating that the interface device 17 is receiving operational power.

The input voltage from the telephone network connection 13 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 the logic circuit 54. The input voltage 48 to logic circuit 54 consists of the output voltage from voltage divider 52. The output of logic circuit 54 is the output voltage 49. The logic circuit 54 will detect when the telephone handset 11 is lifted and the first key dialed is "#". A circuit diagram that illustrates one implementation of logic circuit 54 is shown in Figure 5. As noted above, although the embodiment illustrates the use of the "#" key as the switching input signal, other keys, sequences of keys, voice or audio commands, or additional specialized keys added to a traditional telephone or elsewhere in the system could be used to provide this function.

As shown in the logic circuit diagram in Figure 5, the logic circuit generally comprises three functional components: a decoding circuit 32; a telephone status detect circuit 99; and a switching circuit 96. The decoding circuit 32 decodes input signals from the telephone 11 to provide an output logic signal representing when the special input signal for requesting Internet telephony has been input into the telephone (the correct key output 92). The telephone status detect circuit 99 provides an output signal indicating that the telephone 1 1 is off hook (the off hook output 95). These two signals are fed into the switching circuit 96, which provides a preferably logic high output signal when the telephone is off hook and the proper key has been input (the switch output 97). The switching circuit further determines whether this key was selected in the correct sequence, preferably as the first key input to the telephone 11 after the phone is taken off hook.

Referring now specifically to the decoding circuit 32, the major components of the decoding circuit 32 are a dual tone, multi-frequency (DTMF) signal processor 33, and a digit decoding unit 35 consisting of two inverters 36, a quad AND gate 37, and an inverter 38. The DTMF signal processor 33 decodes all tones on the telephone input line 48. Output data lines from the DTMF signal processor 33 are input to the decoding unit 35, which outputs a correct key output signal 92 at the AND gate 37 when a "#" key has been input to the telephone. A decode signal 93 is provided by the DV output 90 from the DTMF signal processor 33, which goes high (5V) when a digit has been successfully decoded, and is then inverted by inverter 38 to provide a logic low decode signal 93, as will be described more fully below. The DTMF signal processor 33 shown is preferably an HT9170 manufactured by Holtek, but many comparable chips are available as will be recognized by these of skill at the art. Furthermore, although a circuit for detecting telephone codes have been shown, it will be apparent to one of ordinary skill in the art that voice recognition chips, other types of audio detect circuits and comparators could be used to provide the function. Furthermore, although an integrated circuit is shown, discrete logic components, such as transistor or other switching devices, could be used to implement the function.

Referring again to FIG. 5, the telephone status detect circuit 99 generally comprises a comparator circuit for determining when the voltage on the tip and ring lines of the telephone 11 has changed. In this embodiment, the comparator function is provided by an op-amp 45 which is configured to function as a comparator to detect when the telephone handset is on-hook or off-hook. The voltage between the tip and ring lines input into the telephone network jack 13 is typically 48 volts when the telephone 11 is on-hook. The input voltage 48 is connected to the inverting input of op-amp 45. The op- amp 45 compares the input voltage 48 to 6.5 volts, and if the input voltage 48 is higher than 6.5 volts, the op-amp 45 will output a signal of approximately 1.5 volts. When the telephone 11 is off-hook, the input voltage 48 will typically fall in the range of 3-5 volts. The op-amp 45 functioning as a comparator senses the voltage fall, and outputs a "high" voltage of approximately 8 volts. The output of op-amp 45 is reduced by the voltage divider 46, and then input into AND gate 44. When telephone 11 is returned to the on- hook position, the output of op-amp 45 returns to approximately 1.5 volts. The op-amp 45, therefore, provides an off-hook signal 95 which is logic high when the telephone 11 is off hook.

The correct key output 92, the decode signal 93, and the off hook signal 95 are all fed to a switching circuit 96. The switching circuit 96 provides a logic high switch output 97 at the output of the logic circuit 54 whenever the telephone 11 is off hook and the first key dialed is a "#". The switching circuit 96 preferably comprises two J-K flip flops 39 and 41, two AND gates 42 and 44, and two inverters 40 and 43. The correct key output 92 is input directly into the J input of J-K flip-flop 39, and is inverted by inverter 40 and then input into the J input of J-K flip-flop 41. The K input of both J-K flip-flops 39 and 41 are tied to ground. The decode signal 93 provides the clocking function for both J-K flip-flops 39 and 41. The inverted output Q* from J-K flip-flop 41 and the output Q from flip-flop 39 are input into the AND gate 42. The AND gate 42 will provide a logic high switch output 97 whenever the output Q of flip-flop 39 and the output Q* of the flip flop 41 are logic high.

The off hook signal 95 is fed to the CL input of J-K flip flop 39, thereby clearing the output of the flip flop 39 whenever the telephone 11 is on hook, and preventing a logic high at the Q output of the flip flop 39. The CL input of the J-K flip flop 41 is provided by the output of AND gate 44. The output of AND gate 44 will be low whenever either of the inputs to the AND gate 44 is low. Therefore, the CL input of the J-K flip flop will be activated whenever the telephone 11 is on hook (the off hook signal 95 is logic low), whenever the output of the AND gate 42 is high (inverted by inverter 43 before being input to the AND gate 42), or both. In operation, the flip flop 41 provides a logic high signal to one input of the AND gate 42 when the first key is decoded. The flip flop 39 provides a logic high signal to an input of the AND gate 42 whenever a "#" key is detected. The switch output signal 97 of logic circuit 54 will only go high (5 V) when the telephone 11 is off-hook and the first digit dialed is the "#" key. If the first key pressed is not the "#" key, any subsequent combination of keys will not turn the output of logic circuit 54 high, even if the "#" is pressed after the first key dialed. Figure 9 shows the derivation of this function of logic circuit 54 according to the intermediate logic of the DTMF signal processor 33, quad AND gate 37, AND gate 44, J-K flip-flop 41, J-K flip- flop 39, and AND gate 42. Any blanks in the truth table shown in Figure 9 indicate logic circuit 54 is indifferent to the truth state of the labeled inputs. Figure 9 traces the logic of logic circuit 54 through two example scenarios, Scenario 1 and Scenario 2.

In Scenario 1, the switch output signal 97 of logic circuit 54 is false, or low, (~0 V) initially. The telephone 11 is taken from the on-hook state to the off-hook state, and the first number dialed is the "#" key. Once the "#" key is pressed, the switch output signal 97 of logic circuit 54 will go high. Once telephone 11 is returned to the on-hook state, the switch output signal 97 of logic circuit 54 is returned to the original state of false.

In Scenario 2, the switch output signal 97 of logic circuit 54 is again false, or low, initially. The telephone 11 is taken from the on-hook state to the off-hook state, and the first number dialed is the "1" key. Once the "1" key is pressed, the output of logic circuit 54 will remain low, even if the "#" key is pressed any time later during the telephone call. Once telephone 11 is returned to the on-hook state, the output of logic circuit 54 is returned to the original state of false. Although a specific logic circuit 54 has been shown, it will be apparent to one of ordinary skill in the art that logic circuits which provide the functionality described could be easily constructed having different types of logic gates, transistors or other electronic components. Furthermore, the circuit could be embodied in an application specific integrated circuit, instituted all or in part through various types of programmable gate arrays, or provided by other programmable devices such as microprocessors or microcontrollers.

Under the "normal" configuration, when the microphone signals are automatically routed to the PC's microphone jack 15, the output of logic section 54 will be low, or approximately zero volts, as indicated in the truth table of FIG. 9. The audio output from the PC is automatically routed to the external speakers 19, and the telephone 11 is directly connected with the telephone network 12; the telephone 11 is on-hook, the voltage between the two wires of the telephone network input 13 is approximately 50 volts. The invention utilizes diodes 59 to rectify the voltage, in case the polarity on the two telephone lines on RJ-11 jack 13 has been reversed. 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 "true" state and corresponding "high" voltage switch output signal 97 from a logic circuit 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 disconnects the telephone 11 from the telephone network 12 and connects the telephone 11 to a filtered power supply 64 preferably of substantially 9 volts dc. Current from the relay 62 passes through a light emitting diode (LED) 66 or other indicator device to indicate that the telephone 11 is disconnected. Second, the "high" voltage from the logic circuit 54 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 from the transistor 68, 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 15 and speaker jack 16 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 interface device functions in "normal" mode, with the telephone 11 connected to the telephone network 12, a typical 100 VAC signal will result in no more than 50 mV AC signal on either microphone jack 15 or speaker jack 16. After the interface device is switched to "computer phone" mode, transistor 70 will become conducting, and the current from the filtered 9 volt power supply 64 can pass through the telephone 11, 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 handset of the telephone 11 has been lifted and the "#" key was the first key pressed, this means the user must want to use the telephone as the audio interface with the personal computer. The user may want to use the telephone as the audio interface to conduct internet telephony. If the user wishes to place a phone call for Internet telephony such as PC-to-phone or even PC-to-PC calling, audio analysis software on the personal computer could be utilized to decode subsequent DTMF tones to determine the telephone number dialed. Alternatively, voice recognition software on the personal computer could be utilized to determine how to route the call according to the user's voice commands.

Switching the interface device 17 to "computer phone" mode 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 two relays, a single pole single throw relay 81 and a second dual 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 18 and speakers 19. The relay 82 is "normally closed" during "normal" operation, and under the normally closed position the ground for the external speakers 19 and microphone 18 is connected to the ground of the personal computer.

When the relay 82 is activated by the interface device 17 switching to "computer phone" operation, 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 14. The relay 81 is "normally open" during "normal" operation of the interface device 17, isolating the secondary side of the transformer from the external speakers 19. Furthermore, although a transformer is shown, it will be apparent to one of ordinary skill in the art that other amplification and isolation devices such as op-amps or other circuit elements could be used instead of a transformer. 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 14 and the handset of the telephone 11.

The embodiment shown in FIG. 4 is configured for use with stereo speakers and a condenser microphone both connected to a sound card with stereo cables. In this configuration, therefore, the speakers would provide stereo sound. Condenser microphones require external power, which is generally provided by the tip and ring lines of the connection cable, and condenser microphones are commonly used as the audio input with personal computers. 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.

In accordance with the second embodiment of the present invention shown in Figure 6, the interface device 117 can be placed inside the case of a personal computer. Externally, the interface device 117 includes a plurality of connectors for connecting the internal interface device 117 between the telephone 111, the telephone network 112, an external microphone 118, and external speakers 119. An audio output jack 122 and audio input jack 123 are provided to connect the interface device 117 to the computer's internal sound signals. Two RJ-11 connectors, a telephone jack 125 and a telephone network jack 113 provide connection points for connecting the telephone handset 111 and the telephone network 112, respectively. Filtered power to the interface device 117 can be obtained from the personal computer's internal power supply.

Internally, the interface device 117 comprises an internal signal converter circuit board 130. The internal signal converter circuit board 130 includes the same functional blocks as the circuit board 30 described above and shown in FIG. 3. Generally, the signal converter circuit board 130 includes 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 first key dialed is the "#" key, and a system to switch between "normal" operation of the interface device, wherein the personal computer's audio signals are passed directly to the microphone and speakers, to "computer phone" operation, wherein the audio signals are passed directly between the personal computer's audio connections and the telephone handset, and the external microphone and speakers are disconnected.

A circuit diagram that illustrates one implementation of the signal converter board 130 is shown in Figure 7. This implementation will be appreciated by those skilled in the art, and features of this particular implementation that are different from the first embodiment shown in Figure 3 are described in detail below. Many other implementations are possible that can provide the same functionality.

Audio out left 131 and audio out right 132 signals are input from the personal computer motherboard or other sound device internal to the PC into a dual pole dual throw relay 133. When the relay 133 is not activated and negligible (<0.1 mA) current is flowing through the coil of relay 133, the audio out left 131 and audio out right 132 signals are directly connected to the audio output jack 123. When the relay 133 is activated and significant current is flowing through the coil of relay 133, audio out right 132 is connected to a center-tapped transformer 134. Audio in tip 135 and Audio in ring 136 signals are input from the personal computer motherboard or other internal sound device into a dual pole dual throw relay 137. When the relay 137 is not activated, the audio in tip 131 and audio in ring 132 signals are directly connected to an audio input jack 122. When the relay 137 is activated, audio in ring 136 is connected to a center- tapped transformer 134.

Audio out ground 139 and audio in ground 140 are input from the personal computer motherboard or other sound device internal to the PC into a dual pole dual throw relay 141. When the relay 141 is not activated, audio out ground 139 and audio in ground 140 are directly connected to an audio output jack 123 and an audio input jack 122, respectively. When the relay 141 is activated, both audio out ground 139 and audio in ground 140 are connected to a center-tapped transformer 134. Furthermore, although relays 133, 137, and 141 are shown, it will be apparent to one of ordinary skill in the art that other switching devices, analog switches, or other circuit elements combined with software control in the computer could be used instead of relays and switching transistors.

In accordance with the third embodiment of the present invention shown in Figure 8, the interface device 217 can be placed inside a personal computer or general purpose computing device Externally, the interface device 217 mcludes a plurality of connectors for connectmg the internal interface device 217 between the telephone 211 and the telephone network 212 Two RJ-11 connectors, a telephone jack 225 and a telephone network jack 213 provide connection pomts for connecting the telephone handset 211 and the telephone network 212, respectively Filtered power to the interface device 217 can be obtamed from the personal computer's internal power supply

Internally, the interface device 217 comprises an internal signal converter circuit board 230 mcludmg a voltage detection function for monitoring voltage on the telephone lme 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 first key dialed is the "#" key, and a system to switch between "normal" operation of the interface device, wherem the personal computer's audio signals are passed directly to the internal microphone and speakers, to "computer phone" operation, wherem the audio signals are passed directly between the personal computer's audio connections and the telephone handset, and the internal microphone and speakers are disconnected

A circuit diagram that illustrates one implementation of the signal converter board 230 is shown m Figure 9 This implementation will be appreciated by those skilled m the art, and features of this particular implementation that are different from the first and second embodiments shown m Figure 4 and Figure 7, respectively, are described m detail below Many other implementations are possible that can provide the same functionality

Audio out left 231 and audio out πght 232 signals are mput from the personal computer motherboard or other sound device internal to the PC mto a dual pole dual throw relay 233 When the relay 233 is not activated the audio out left 231 and audio out πght 232 signals are directly connected to internal speakers left 234 and internal speakers πght 235 channels, respectively When the relay 233 is activated current flows through the coil of relay 233, audio out πght 235 is connected to a center-tapped transformer 236 Audio m left 237 and audio m πght 238 signals are input from the personal computer motherboard or other internal sound device mto a dual pole dual throw relay 239 When the relay 239 is not activated, the audio in left 237 and audio m πght 238 signals are directly connected to the internal microphone left 240 and internal microphone πght 241 channels, respectively When the relay 239 is activated, audio m nght 237 is connected to a center-tapped transformer 236 Audio out ground 242 and audio in ground 243 are input from the personal computer motherboard or other sound device internal to the PC into a dual pole dual throw relay 244. When the relay 244 is not activated, audio out ground 242 and audio in ground 243 are directly connected to the internal speakers ground 245 and internal microphone ground 246, respectively. When the relay 244 is activated, both audio out ground 242 and audio in ground 243 are connected to a center-taped transformer 236. Furthermore, although relays 233, 239, and 244 are shown, it will be apparent to one of ordinary skill in the art that other switching devices, analog switches, or other circuit elements alone or combined with software control in the computer could be used instead of relays and switching transistors.

Although the present invention has been shown in three separate embodiments employing separate interface boards and circuits, it will be apparent to one of ordinary skill in the art that connectors, circuitry and software necessary to implement the invention could be added directly to a sound card, a mother board, or other internal printed circuit board in a personal or general purpose computer without the need for a separate interface. Furthermore, the required circuitry could be added to a specialized telephone or "web-phone" device. In addition, the general purpose computing device in the third embodiment shown in Figure 8 could be installed inside a wireless phone that is connected to a wireless data network. The on-hook status could be represented as a voltage signaling the wireless phone is not actively transmitting data. Coπespondingly, the off-hook status could be represented internal to a wireless phone as a voltage signaling the wireless phone is either actively transmitting data or that a telephone call is about to be placed.

While prefeπed 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

What is claimed:

1. A method for switching audio signals between a computer and a telephone, the

method comprising:

detecting an off-hook condition for the telephone;

detecting that a predetermined input signal has been provided; and

switching the audio signals from the computer to the telephone when the off-hook

condition is detected and the predetermined input signal has been provided.

2. The method as defined in claim 1, wherein the predetermined input signal is

provided by activating a key on a standard telephone keypad.

3. The method as defined in claim 1, wherein the predetermined signal is an audio

signal.

4. The method as defined in claim 1, wherein the predetermined signal is provided by

a specialized input key.

5. A switching apparatus for switching the path of input and output audio signals

between a computer and a telephone, the switching apparatus comprising:

a switch detection circuit responsive to a predetermined switch input signal to

produce a switch detect output signal;

a telephone off-hook circuit responsive to the telephone being taken off hook to

produce a telephone active signal; a switching circuit activated by the switch detect output signal and the telephone

active signal, the switching circuit being configured to route the input and output audio

signals from a speaker and microphone coupled to the computer sound card to a speaker

and microphone in a handset of the telephone when the switch detect output signal and

the telephone active signals are received.

6. The switching apparatus as defined in claim 5, wherein the switch detection circuit

comprises a DTMF detection circuit activated by activating a predetermined key on a

telephone keypad.

7. The switching apparatus as defined in claim 5, wherein the telephone off-hook

circuit comprises a comparator circuit, the comparator circuit being activated in response

to a voltage state change on an input line from the telephone.

8. The switching apparatus as defined in claim 6, wherein the switching circuit is

further responsive to a decode signal, the decode signal indicating that the DTMF signal

has been decoded.

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

coupled to a mother board of the computer.

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

incorporated in the telephone.

11. An interface device configured to couple a telephone to an internet data link for

use in internet telephony, the interface device comprising:

a first connector for coupling a computer to the interface device;

a second connector for coupling a telephone to the interface device;

a switching circuit configured to receive a telephone active signal indicating that

the telephone is off-hook and to receive a switch detect signal indicating that a

predetermined key was the first key activated on the telephone keyboard after the

telephone was taken off-hook, and to switch audio signals from a computer sound card of

the computer to the telephone.

12. The interface device as defined in claim 11, wherein the first connector facilitates

connections to a computer sound card.

13. The interface device as defined in claim 11, further comprising a connector for an

external microphone.

14. The interface device as defined in claim 11, further comprising a connector for an

external speaker.

15. The interface device as defined in claim 11, further comprising a connector for an

input telephone line.

16. The interface device as defined in claim 11, wherein the telephone active signal is

provided by a comparator circuit coupled to the telephone tip and ring line.

17. A telephone for use in internet telephony, the telephone comprising:

a connection to a telephone input line;

a computer sound card for converting received digital signals to audio signals and

transmitted audio signals to digital signals;

a switching circuit responsive to a telephone active signal and a predetermined

input signal to switch the received and transmitted audio signals to a speaker and

microphone coupled to the telephone.

18. The telephone as defined in claim 17, wherein the predetermined input signal is

produced by activating the pound key on the telephone keypad.

19. The telephone as defined in claim 17, wherein the predetermined input signal is

produced by a specialized switching device.

20. The telephone as defined in claim 17, wherein the predetermined input signal is

provided by a voice command.

21. An apparatus for providing internet telephony through the handset of a telephone,

the interface device comprising:

a connection point for a computer sound card coupled to a computer;

a connection point for a telephone;

a connection point for an external speaker system;

a connection point for an external microphone; a connection point for an incoming telephone line;

a connection point for a modem; and

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

route the audio signals from a sound port of the sound card to the telephone

handset when the telephone is off-hook and a predetermined input signal has been

provided to the switching circuit.

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

component coupled between the telephone and the computer.

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

case housing the computer.

24. The apparatus as defined in Claim 21, wherein the interface is incorporated in the

telephone.

25. A method for providing internet telephony through a telephone, the method

comprising the following steps:

establishing an internet data link to a modem coupled to an input communications

line;

detecting that a telephone is off-hook;

providing a predetermined input signal; switching an audio signal path from the computer to the telephone when the

telephone is off-hook and the predetermined input signal has been received thereby

allowing a user to use the telephone to talk over the internet.

26. The method as defined in claim 25, further comprising the step of monitoring a

voltage on the tip and ring lines of the telephone to determine that the telephone is off

hook.

27. The method as defined in claim 25, further comprising the step of deterrnining that

a predetermined input key has been selected by dividing the input signal with a DTMF

divide circuit, waiting for a decode signal, and deterrnining that the input signal is the

first input key.

28. The method as defined in claim 25, further providing the step of determining that

the predetermined input signal was the first input signal selected on the telephone keypad

prior to switching.

29. A method for switching audio signals between a telephone and a computer, the

method comprising:

defining a normal state wherein an input audio signal is passed to an external

speaker coupled to the computer and an output audio signal is passed to a microphone

coupled to the computer; defining a computer telephone state wherein the input audio signal is passed to the

speaker of a handset coupled to the telephone and the output audio signal is passed to a

microphone in the handset;

detecting when the telephone is off hook;

detecting when a predetermined signal has been provided;

switching from the normal state to the computer telephone state when the

telephone is off hook and the predetermined signal has been provided; and

returning to the normal state when the telephone is on hook.