Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-12-21
2002-04-30
Nguyen, Lee (Department: 2683)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S557000, C379S052000, C379S093180
Reexamination Certificate
active
06381472
ABSTRACT:
TECHNICAL FIELD
The present invention relates to techniques for effectively coupling a data communication device for a speech or hearing impaired user, such as a TDD or TTY, to a digital wireless telephone unit, to enable communication for the impaired user through a digital wireless telephone network.
BACKGROUND
Modern society offers people many opportunities and in fact places many demands on people to communicate with each other, often over great distances. One of the most common forms of communication involves conversational speech communicated between two or more parties through a telephone network. Today, such telephone communication is virtually ubiquitous throughout the modern world. A person can simply take a telephone off-hook at one location, dial a destination telephone number, and if someone answers the called telephone, the caller can converse with the other party anywhere in the world.
The communication of speech over the telephone network depends on both parties having good auditory abilities, to speak and hear each other. Persons with hearing and/or speech impairments often can not utilize voice-grade telecommunications services. For many years, these problems barred hearing or speech impaired individuals from communicating via the telephone network.
Data devices transmitting messages in the audio range carried by the telephone network were developed to allow such individuals to communicate through the network. The most common device for this purpose, a telecommunication device for the deaf “TDD” or similar device, typically appears as a simple computer or teletype (TTY) terminal. The TDD or TTY utilizes Baudot code to transmit and receive low speed character data. Typically, one user keys in conversational information on one TDD, which sends character data through the telephone network. Another user's TDD receives and displays the information. These TDD or TTY devices allow individuals having hearing or speech impairments to send and receive communications over any media that can transport the low-speed Baudot code. Many people with speech or hearing impairments and people they communicate with have used TDDs for some years now and have become quite accustomed to use of such devices in their everyday lives.
The Baudot code used by TDDs transmits characters represented by five binary information bits, which means that the character set is limited to 32 characters. To convey more characters, one character is designate “LTRs” indicating that subsequent characters represent letters, and another character is designated “FIGs” indicating that subsequent characters represent numbers.
The TDD or TTY device originally was designed for communication over analog telephone lines. Such a device sends the ones (1s) and zeros (0s) representing the five-bit binary Baudot character codes as separate audio tones, commonly referred to as “MARK” and “SPACE” tones in a form of frequency shift key (FSK) modulation. The tone frequencies (1400 Hz and 1800 Hz) originally were selected to enable accurate transport thereof through the telephone network. The telephone network itself is optimized to carry a limited portion of the audio spectrum, which normally contains the majority of audible information for human speech, typically in a range of approximately 300-4000 Hz. As such, the data communication devices commonly used by speech or hearing impaired individuals typically send and receive information in the form of FSK MARK and SPACE tones within the narrow audio bandwidth of the analog telephone service.
Use of a TDD/TTY data device enables the hearing impaired to communicate from any location having an analog telephone line to any other location having an analog line connection to a compatible device. As the telephone network has grown, this TDD service based on a telephone line connection has enabled people to use the TDD from almost any fixed location in the world. The main limitation has been that the user must communicate with someone having a compatible device and line connection. People who routinely communicate with hearing or speech impaired individuals have obtained compatible data devices. Many emergency services (e.g. E911), telephone companies, other businesses and government agencies also have installed compatible equipment to allow the impaired individuals to use their TDDs/TTY to communicate with operators/agents or even to interface with automated attendant systems for various purposes.
Modern society, however, also is becoming increasingly mobile. Many new communications services have emerged, to allow people to communicate freely as they roam, without the need for a fixed network connection. As the services have evolved, however, they have created new problems of access for persons with speech or hearing impediments.
To enable communications for people on the go, a number of wireless mobile services have evolved and grown exponentially. Analog cellular telephone service is now quite common throughout much of the developed world and continues to serve many customers. In recent years, a number of digital wireless communications technologies have begun to compete with and gradually replace the analog wireless service. All of these services enable a customer to make and receive wireless, voice-grade telephone calls from virtually any point in the carrier's service area. With roaming agreements, customer may obtain the mobile service from almost anywhere in a country or continent.
The digital versions of the mobile services offer a number of advantages over the older analog technology, most notably improved performance, much greater security/privacy, alternate communication of data, and easier implementation of new enhanced service features. In view of the advantages, the trend in the industry is to migrate over from the old analog wireless service to the newer digital wireless services.
As noted, the TDDs send and receive analog tone signals to carry the typed textual information. This technique is quite effective over the voice-grade landline telephone network. Users with TDDs and similar TTY devices also have had success communicating over analog cellular telephone networks. However, more modern digital wireless networks do not accurately transport the tone signals. The digitizing and compressing of the audio information and the associated noise reduction processing necessary in a digital wireless network badly distort the FSK MARK and SPACE tone signals used by TDD/TDY devices. This prevents persons wanting to continue to use their TDDs or TTYs from using the more modern digital wireless telephone systems, obtaining the benefits thereof or accessing many of the more modern service features available through the new digital mobile telephone networks.
Today there are many more modern data devices available that provide faster data communications than the TDDs or TTYs. Personal computers (PCs), in particular, offer fast textual data processing and communication in combination with multimedia capabilities. Most digital wireless stations and wireless communication networks support data communication, for example to and from laptop PCs. These communications carry the data over the air interface as digital data, without analog modulation or the need to pass analog signals back and forth through the noise reduction and vocoder circuitry. Such data devices and wireless communications provide far superior communications and increased mobility, and one solution for current users of TDD/TTYs might be to upgrade to these more modern data devices and communication technologies.
However, many people who have used the TDDs or the like for a substantial time are very reluctant to upgrade to the newer data devices. They are familiar with the TDDs and the conversation-like textual communication that those devices provide. They may be uncomfortable with the more complex operations of PCs. Also, anyone communicating with a person with an impairment needs to have a compatible device. Many already have TDD or TTY compatible equipment. An impaired user seeking to upgrade to new
LaMedica, Jr. Louis
Whritenour Lee J.
Bell Atlantic Mobile Inc.
McDermott & Will & Emery
Nguyen Lee
LandOfFree
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