# US 7,411,941 B2 · Text telephone modem communications over packet networks

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 7,411,941 B2
- Document ID: US7411941B2
- Status: Granted
- Kind: B2
- Application number: 11/036,627
- Filed: 2005-01-13
- Published: 2005-09-08
- Granted: 2008-08-12
- Earliest claimed: 2004-03-02
- Assignees: Mindspeed Technologies, Inc.
- Inventors: Keith T. Chu; Jason B. Brent
- Web page: https://patentgrep.com/patent/US7411941B2

## CPC

- H04L 12/66: Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
- H04L 9/40: Network security protocols
- H04M 11/06: Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
- H04L 69/18: Multiprotocol handlers, e.g. single devices capable of handling multiple protocols
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08)

## Abstract

A modem detection method is provided for use by a first gateway, the first gateway capable of communicating with a second gateway over a packet network. The method comprises setting the first gateway to a voice mode having a first coding scheme, encoding an input signal using the first coding scheme to generate a first encoded input signal, transmitting the first encoded input signal to the second gateway over the packet network, looking for a first tone in the input signal while the first gateway is in the voice mode, wherein the first tone is indicative of a beginning of a character, detecting the first tone in the input signal; setting the first gateway from the voice mode to a modem mode in response to the detecting; and transmitting the input signal to the second gateway according to the modem mode.

## Claims

### Claim 1

A text telephone modem detection method for use by a first gateway, said first gateway being capable of communicating with a second gateway over a packet network, said method comprising:
setting said first gateway to a voice mode having a first coding scheme;
encoding an input signal using said first coding scheme to generate a first encoded input signal, while said first gateway is in said voice mode;
transmitting said first encoded input signal to said second gateway over said packet network, while said first gateway is in said voice mode;
looking for a first tone in said input signal while said first gateway is in said voice mode, wherein said first tone is indicative of a beginning of a text telephone modem character, and wherein said text telephone modem character comprises said first tone;
detecting said first tone in said input signal while performing said looking;
setting said first gateway from said voice mode to a text telephone modem mode in response to said detecting;
providing a silence period, after a switching silence caused by said setting said first gateway from said voice mode to said text telephone modem mode, so as to prevent a detection of said first encoded input signal by said second gateway as said beginning of said text telephone modem character; and
transmitting said input signal to said second gateway over said packet network, after said silence period, according to said text telephone modem mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein said text telephone modem mode has a second encoding scheme, and wherein the method further comprises:
encoding said input signal using said second coding scheme to generate a second encoded input signal, while said first gateway is in said text telephone modem mode; and
transmitting said second encoded input signal to said second gateway over said packet network, while said first gateway is in said text telephone modem mode.

### Claim 3 (depends on 2)

The method of claim 2 further comprising:
delaying said input signal in a delay line for a pre-determine period of time to generate a delayed input signal while said first gateway is in said voice mode;
transmitting said delayed input signal to said second gateway over said packet network according to said text telephone modem mode, prior to said transmitting said input signal to said second gateway over said packet network according to said text telephone modem mode.

### Claim 4 (depends on 3)

The method of claim 3, wherein said delay line is less than a text telephone modem character bit time.

### Claim 5 (depends on 3)

The method of claim 3, wherein said delay line is less than one half of a text telephone modem character bit time.

### Claim 6 (depends on 1)

The method of claim 1, wherein said text telephone modem mode has a modem demodulator, wherein the method further comprises:
demodulating said input signal using said modem demodulator to generate a demodulated input signal, while said first gateway is in said text telephone modem mode; and
transmitting said demodulated input signal to said second gateway over said packet network, while said first gateway is in said text telephone modem mode.

### Claim 7 (depends on 1)

The method of claim 1 further comprising:
verifying said input signal is a modem signal after said setting said first gateway to said text telephone modem mode; and
switching said first gateway to said voice mode if said verifying fails.

### Claim 8 (depends on 1)

The method of claim 1, wherein said looking looks for said first tone and one or more additional tones in said input signal while said first gateway is in said voice mode, wherein each of said one or more additional tones is indicative of said beginning of said text telephone modem character, and wherein said detecting detects said first tone or said one or more tones in said input signal while performing said looking.

### Claim 9

A first gateway capable of detecting a text telephone modem, said first gateway having a voice mode and a text telephone modem mode, said first gateway being capable of communicating with a second gateway over a packet network, said first gateway comprising:
an encoder configured to encode an input signal using a first coding scheme to generate a first encoded input signal, while said first gateway is in said voice mode;
a transmitter configured to transmit said first encoded input signal to said second gateway over said packet network, while said first gateway is in said voice mode;
a detector configured to look for a first tone in said input signal while said first gateway is in said voice mode, wherein said first tone is indicative of a beginning of a text telephone modem character, and wherein said text telephone modem character comprises said first tone;
wherein said detector is configured to detect said first tone in said input signal while looking for said first tone, wherein said first gateway is configured from said voice mode to said text telephone modem mode in response to detecting said first tone,
wherein said first gateway is configured to provide a silence period, after a switching silence caused by said configuring said first gateway from said voice mode to said text telephone modem mode, so as to prevent a detection of said first encoded input signal by said second gateway as said beginning of said text telephone modem character; and
wherein said transmitter is configured to transmit said input signal to said second gateway over said packet network, after said silence period, according to said text telephone modem mode.

### Claim 10 (depends on 9)

The first gateway of claim 9, wherein said text telephone modem mode has a second encoding scheme, and wherein said encoder is configured to encode said input signal using said second coding scheme to generate a second encoded input signal, while said first gateway is in said text telephone modem mode, and wherein said transmitter is configured to transmit said second encoded input signal to said second gateway over said packet network, while said first gateway is in said text telephone modem mode.

### Claim 11 (depends on 10)

The first gateway of claim 10 further comprising:
a delay line configured to delay said input signal for a pre-determine period of time to generate a delayed input signal while said first gateway is in said voice mode;
wherein said transmitter is further configured to transmit said delayed input signal to said second gateway over said packet network according to said text telephone modem mode, prior to said transmitting said input signal to said second gateway over said packet network according to said text telephone modem mode.

### Claim 12 (depends on 11)

The first gateway of claim 11, wherein said delay line is less than a text telephone modem character bit time.

### Claim 13 (depends on 11)

The first gateway of claim 11, wherein said delay line is less than one half of a text telephone modem character bit time.

### Claim 14 (depends on 9)

The first gateway of claim 9 further comprising:
a modem demodulator;
wherein said modem demodulator is configured to demodulate said input signal to generate a demodulated input signal, while said first gateway is in said text telephone modem mode, and wherein said transmitter is further configured to transmit said demodulated input signal to said second gateway over said packet network, while said first gateway is in said text telephone modem mode.

### Claim 15 (depends on 9)

The first gateway of claim 9, wherein said first gateway is configured to verify that said input signal is a modem signal after setting said first gateway to said text telephone modem mode, and wherein said first gateway is further configured to switch to said voice mode if said input signal is not verified to be a modem signal.

### Claim 16 (depends on 9)

The first gateway of claim 9, wherein said detector is configured to look for said first tone and one or more additional tones in said input signal while said first gateway is in said voice mode, wherein each of said one or more additional tones is indicative of said beginning of said text telephone modem character, and wherein said detector is configured to detect said first tone or said one or more tones in said input signal while performing said looking.