Abstract:
An apparatus and method communicate TTY calls by detecting a TTY call, determining that a digital display on a first telecommunication terminal is to be used to display TTY information of the call from a second telecommunication terminal and that audio information will be transmitted to the second telecommunication terminal, converting the TTY information from the second telecommunication terminal to digital display information, transmitting the digital display information to the first telecommunication terminal, and muting an incoming call audio path from the second telecommunication terminal to the first telecommunication terminal.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to telecommunication systems and methods in general, and in particular, to the control of telecommunication calls involving TTY transmissions.  
       BACKGROUND OF THE INVENTION  
       [0002]     TTYs (also known as TDDs) are text terminals that people with hearing impairments use in order to communicate over telephone lines. In the United States, the most commonly used TTY communication protocol is the technique specified by ANSI/TIA/EIA 825 (“A 45.45 Baud FSK Modem”). Relevant characteristics of this protocol include the following:  
         [0003]     (1) TTYs are silent when not transmitting. Unlike fax machines and computer modems, TTYs have no “handshake” procedure at the start of a call, nor do they have a carrier tone during the call. Although this approach tends to limit the speed of transmission, it has the advantage of permitting TTY tones, DTMF (Dual Tone Multi-Frequency signals, also known as “touch tones”), and voice to be intermixed on the same call.  
         [0004]     (2) Operation is “half duplex.” TTY users must take turns transmitting, and typically cannot interrupt each other. If both people try to type at the same time, their TTYs will show no text at all, or will show text that is gibberish. There is no automatic mechanism that lets TTY users know when a character they have typed correctly has been received incorrectly. To avoid this problem, a user normally types a message and then types “GA” (for go ahead). This does solve the problem of half duplex operation but results in a slow, jerky operation which tends to limit spontaneous interaction.  
         [0005]     (3) Each TTY character consists of a sequence of seven individual tones. The first tone is always a “start tone” at 1800 Hz. This is followed by a series of five tones, at either 1400 or 1800 Hz, which specify the character. The final tone in the sequence is always a “stop tone” at 1400 Hz. The “stop tone” is a border that separates this character from the next. Each of the first six tones is 22 milliseconds in duration. The final “stop tone” may also be 22 milliseconds, but is permitted to be as long as 44 milliseconds. This means that the duration of each TTY character is at least 154 milliseconds, which works out to approximately six and a half characters per second. (The description of this as a “45.45 Baud” protocol is based on the number of 22-millisecond tones that can be transmitted in one second, not the number of characters.)  
         [0006]     From a usability perspective, one of the benefits to using a half-duplex, carrier-free protocol for TTYs is that it is possible to intermix voice and TTY transmissions on the same call. This is important because nearly half the people who use TTYs are individuals with moderate hearing loss who nevertheless are able to speak clearly; these individuals often prefer to receive with their TTYs and then speak in response, a process commonly referred to as Voice Carry Over or VCO. Another common pattern is for individuals (including those who hear adequately but do not speak clearly) to alternate between TTY and voice on the same call, relying on voice for informal conversation and TTY for critical information such as addresses and credit card numbers.  
         [0007]     From a usability perspective, this protocol also has several disadvantages, including: (1) TTY users must take turns typing to each other, and are unable to interrupt each other. (2) VCO users (individuals who prefer to receive via TTY and then speak in response) need a TTY device or specialized VCO telephone in order to communicate. (3) People who receive a TTY message in their voicemail mailbox (which may include mailbox owners who have no communication disabilities, and therefore no easy access to a TTY), need a TTY device or specialized software to read the message. (4) The absence of handshake tones means that there is no mechanism by which to detect that a person is a TTY user until that person starts typing. (5) The protocol itself, although very robust when used in conjunction with traditional circuit-switched analog or digital telephony systems, tends to be unreliable when used in telephony systems that employ packet switching (e.g., Voice over Internet Protocol networks) or voice-optimized audio compression techniques (e.g., the GSM encoding used in many wireless systems).  
         [0008]      FIGS. 1 and 2  illustrate the problems of performing VCO operations with a standard, 45.45 Baud, TTY such as TTY  102 . To transmit or receive TTY information to other party  109 , user  108  has to place the handset  107  into TTY  102  as illustrated in  FIG. 1 .  FIG. 3  illustrates a pictorial view of a telephone such as shown in  FIG. 1  having telephone  301  and TTY  302 . If user  108  wants to use VCO operations, user  108  has to receive TTY information as illustrated in  FIG. 1 , but speaks by first removing handset  107  from the acoustic coupler of TTY  102  as illustrated in  FIG. 2  and then speaking. To once again receive TTY information, user  108  has to place handset  107  back into the acoustic coupler of TTY  102  before other party  109  transmits TTY information to TTY  102 . This type of VCO operation is awkward at best.  
         [0009]     The 45.45 Baud FSK protocol has been used in United States TTYs since 1963, and is based largely on the protocol that was used in military teletypewriters during the Second World War. Quite obviously, modern techniques would permit the development of new protocols that retain the advantages of the current protocol, while eliminating the disadvantages. Although many new protocols with excellent capabilities have been proposed, an important barrier stands in the way of their general acceptance: by some estimates, as many as 40,000,000 TTYs that use the 45.45 Baud protocol have been manufactured and distributed since 1963. This constitutes an enormous embedded base that cannot be upgraded or replaced economically. For this reason, it is desirable to solve the usability problems in a manner that does not require the 45.45 Baud protocol, and millions of current-generation TTY devices, to be abandoned.  
         [0010]     Among the above-listed problems associated with the 45.45 Baud protocol, the issue that has been addressed explicitly in prior art concerns the inability of packet switched networks or voice-optimized compression codecs to support reliable TTY communication. Attention has been paid to these problems largely because, in the United States, Section 508 of the Workforce Investment Act of 1998, as well as Sections 251(a)(2) and 255 of the Telecommunication Act of 1996, require telephony systems to be TTY compatible.  
         [0011]     In the prior art, it has been recognized that TTY signals need not be transmitted as audio tones, and may instead be converted and transmitted as digital information in a more reliable non-audio data channel. U.S. Pat. No. 6,351,495 discloses a cellular transmission system where TTY audio signals are recognized and converted to digital information for transmission via the signal transmission portion of the cellular system. Also, in the prior art for VoIP systems, it is known to encode precision tones such as multi-frequency dial tones as digital information and transport this digital information to a destination point via a signaling channel that is distinct from the bearer channel used for encoded voice. One such VoIP system that transports multi-frequency dial tones in this manner is disclosed in U.S. patent application Ser. No. 09/18,909, entitled “Integration of Remote Access and Service”, filed Nov. 22, 2000, and assigned to the same assignee as the present patent application. U.S. patent application Ser. No. 09/18,909 is hereby incorporated by reference. It is important to note, however, that objective of these approaches is to permit the original audio tones to be reconstructed accurately at the receiving location. Although the problem of reliable transport for TTY signals on wireless or VoIP networks is addressed by these approaches, a problem that remains is that a user who receives these transmissions still requires a TTY device or specialized software to translate the transmissions into human-readable text.  
       SUMMARY OF THE INVENTION  
       [0012]     An apparatus and method communicate TTY calls by detecting a TTY call, determining that a digital display on a first telecommunication terminal is to be used to display TTY information of the call from a second telecommunication terminal and that audio information will be transmitted to the second telecommunication terminal, converting the TTY information from the second telecommunication terminal to digital display information, transmitting the digital display information to the first telecommunication terminal, and muting an incoming call audio path from the second telecommunication terminal to the first telecommunication terminal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]      FIGS. 1 and 2  illustrate a prior art arrangement for performing VCO operations;  
         [0014]      FIG. 3  pictorial view of the telephone and TTY terminal of  FIG. 1 ;  
         [0015]      FIGS. 4A, 4B  and  4 C illustrate, in block diagram form, embodiments of systems for implementing the invention;  
         [0016]      FIG. 5  illustrates, in block diagram form, an embodiment of a system for implementing the invention;  
         [0017]      FIG. 6  illustrates, in block diagram form, an embodiment of an IP telephone;  
         [0018]      FIG. 7  illustrates, in pictorial form, an embodiment of a digital telephone; and  
         [0019]      FIGS. 8 and 9  illustrate, in flowchart form, an embodiment of operations performed for implementing the invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]      FIG. 4A  illustrates an embodiment of a system for implementing the invention. Controller  405  provides overall control of TTY  402 , and controller  419  provides overall control of digital telephone  406 . For VCO operation, user  408  will signal telecommunication switching system  401  that user  408  wants to receive TTY information on alphanumeric display  411  and transmit information by speaking into handset  407  of digital telephone  406  as illustrated in  FIG. 4A . An example of a digital telephone such as digital telephone  406  is illustrated in  FIG. 7 . Digital telephone  406  can be an ISDN, IP, or proprietary digital protocol telephone. During this VCO operation, TTY  402  is not used at all, and only digital telephone  406  is required; hence, if user  408  can function well performing only VCO operations, user  408  does not have to have TTY  402 . To perform VCO operations, telecommunication switching system  401  transmits TTY information via control path  414  of telephone link  413  to alphanumeric display  411  and receives voice information from handset  407  via call path  416  of telephone link  413 . In one embodiment, user  408  may use a button of indicators, buttons and keypad  412  to signal telecommunication switching system  401  to start VCO operations. In another embodiment, telecommunication switching system  401  automatically detects TTY information and starts VCO operations.  
         [0021]     To retrieve TTY messages stored on voice message system  417 , user  408  only needs to use digital telephone  406 .  
         [0022]     Full duplex operation is also implemented by the embodiment illustrated in  FIG. 4A . For full duplex operation, user  408  will signal telecommunication switching system  401  that user  408  wants to receive TTY information on alphanumeric display  411  and transmit audio information by via handset  407  of digital telephone  406  as illustrated in  FIG. 4A . Handset  407  is inserted into acoustic coupler  418 . Assuming that other party  409  also has a TTY and digital telephone similar to TTY  402  and digital telephone  406 , respectively, other party  409  will similarly signal telecommunication switching system  401 . TTY information typed by user  408  will be displayed on display  403  of TTY  402  and transmitted via call path  416  to telecommunication switching system  401 . TTY information received from other party  409  via control path  414  will be displayed on display  411  of digital telephone  406 . Other party  409  will function in a similar manner. This full duplex operation allows the simultaneous and spontaneous exchange of TTY information between the two users.  
         [0023]     Full duplex operation is also implemented by the embodiment illustrated in  FIG. 4B . Call path  416  communicates the audio information from TTY  402  to telecommunication switching system  401 . Analog interface  422  provides this audio information that is received from TTY  402 . TTY  402  uses interface  421  to communicate with analog interface  422 . Interfaces  421  and  422  are well known to those skilled in the art. TTY information typed by user  408  will be displayed on display  403  of TTY  402  and transmitted on call path  416  to telecommunication switching system  401 . TTY information received from other party  409  via control path  414  will be displayed on display  411  of digital telephone  406 . Other party  409  will function in a similar manner.  
         [0024]     Full duplex operation is also implemented by the embodiment illustrated in  FIG. 4C . TTY  402  is connected to telecommunication switching system  401  via analog link interface  424  and telephone link  426 . Telecommunication switching system  401  provisions links  413  and  424  as a bridged line appearance resulting in links  413  and  424  being permanently conferenced together and given identical audio path processing. (Bridged line appearances are well know to those skilled in the art.) TTY information typed by user  408  will be displayed on display  403  of TTY  402  and transmitted on call path  423  to telecommunication switching system  401 . Call path  416  is not used. TTY information received from other party  409  via control path  414  will be displayed on display  411  of digital telephone  406 . Other party  409  will function in a similar manner.  
         [0025]      FIG. 5  illustrates an embodiment of a system for implementing the invention. Enterprise switching system  501  is providing service for directly connected telephones  513 - 114  via line circuit  512  and switching network  516 . Telephones  513 - 514  are digital telephone using either an ISDN telephone or proprietary protocol digital telephones. Digital telephones have alphanumeric displays that are controlled by control computer  521  via a signaling/control channel. Digital telephone  514  supports TTY terminal  515 . Further, enterprise switching system  501  is providing call operations for IP telephone  503  and IP telephone  507  via LAN  502 , IP trunk  519 , and switching network  516 . One skilled in the art would readily realize that there would be more wired telephones and IP telephones in a system such as illustrated in  FIG. 5 . IP telephone  503  is illustrated as being able to communicate with a user via handset  506  and TTY terminal  504 . IP telephone  503  also provides visual and other audio alerting means. A WAN or other digital networks well known to those skilled in the art may be used in place of LAN  502 . Control computer  521  controls Enterprise switching system  501 . The operations of processor  523  and memory  522  will be detailed later. TTY controller  506  illustrates an embodiment of a controller for implementing the invention.  
         [0026]     Enterprise switching system  501  is interconnected to public telephone switching network  508  via trunk  517 . For illustration purposes, public telephone switching network  508  is illustrated as being connected to only telephone  509  and TTY terminal  511 . However, one skilled in the art would readily realize that there would be a multitude of telephone equipment connected to public telephone switching network  508 .  
         [0027]      FIG. 6  illustrates, in block diagram form, an embodiment of an IP telephone such as IP telephone  503 . Processor  609  controls the operations of the IP telephone by executing applications stored in memory  601  utilizing data also stored there. Processor  609  communicates information with handset  506  via interface  613  and communicates with LAN  502  via interface  614 . Communication with a TTY terminal is via interface  616 . The IP telephone also has a visual display, buttons, and alerting means to provide signaling to and from the user. These visual displays, buttons, etc. are illustrated as block  611 . Processor  609  communicates with block  611  via interface  617 .  
         [0028]     To perform the operations of an IP telephone, processor  609  executes IP applications  607  stored in memory  601 . The overall control of the IP telephone is provided by execution of operating system  602  by processor  609 . Processor  609  utilizes data  606  for the storage of various types of parameters and information. Buffer  603  is used to provide storage for audio or TTY information. To communicate with interfaces  613 - 617 , processor  609  executes interfaces application  608 .  
         [0029]      FIG. 7  illustrates an embodiment of a telephone set such as IP telephone  503  or digital telephone  514 . With respect to an IP telephone as illustrated in  FIG. 6 , visual display and buttons block  611  would include display  701 , keypad  716 , indicators such as indicators  704 - 706 ,  709 , and  712 , buttons such as  706 - 708 ,  711 , and  714 . The other buttons and indicators illustrated in  FIG. 7  will also comprise block  611  of  FIG. 6 . Handset  702  also would be comparable to handset  506 .  
         [0030]     To illustrate the various embodiments, consider the following example. Control computer  521  receives an incoming call or an outgoing call which computer  521  determines may utilize TTY transmission. Assume that the call is being placed from telephone  509  and TTY terminal  511  to IP telephone  506 . In order to detect the possibility that TTY transmissions may occur, control computer  521  utilizes the data stored in TTY ID equipment block  527  and TTY ID incoming numbers block  528  as disclosed in U.S. patent application Ser. No. 10/406,337, entitled “Apparatus and Method for Transitioning Between TTY and Voice Transmission Modes”, filed Apr. 3, 2003 and assigned to the same assignee as the present patent application. U.S. patent application Ser. No. 10/406,337 is hereby incorporated by reference. If the user of IP telephone  503  has indicated to control computer  521  earlier by actuation of a button such as button  711 , that the user wished to utilize display  701  to receive TTY information rather than TTY terminal  504 , control computer  521  mutes the transmission path from enterprise switching system  501  to IP telephone  503 . Control computer  521  transmits any TTY characters received from TTY terminal  511  as control information that will be displayed on display  701 . This allows the user of IP telephone  503  to utilize either TTY terminal  504  to respond to information being displayed on display  701  or speak the response via handset  506 .  
         [0031]     In another embodiment, control computer  521  will signal the user of IP telephone  503  by utilizing a spare indicator such as indicator  712  to indicate that the incoming call may be a TTY call or by displaying a message on display  701 . In response to this indication, the user can indicate that the display  701  is to be utilized by actuating a button such as button  711 . One skilled in the art will realize that the indicators and the buttons illustrated in  FIG. 7  are assignable to any function by control computer  521 . Control computer  521  stores the fact that button  711  has been actuated in data  529  for later use.  
         [0032]     Digital telephone  514  operates in a similar manner utilizing TTY terminal  515  as was previously described for IP telephone  503 .  
         [0033]     Control computer  521  performs similar functions if it detects that an outgoing call is being made from digital telephone  514  or IP telephone  503  since it would recognize that these terminals were capable of producing TTY transmissions based on information in TTY ID equipment block  527  or actuation of a button.  
         [0034]     Consider another example to further illustrate the embodiments. Assume that a TTY message has been recorded in voice message system  505  for one of the telephones interconnected to enterprise switching system  501 . If control computer  521  determined that the message could be a TTY transmission before its storage in voice message system  505 , control computer  521  stores an indication of this fact. In another embodiment, voice message system  505  may store an indication. In response to such an indication and upon accessing the voice message from voice message system  505 , control computer  521  utilizes TTY controller  506  to convert the TTY information to text information. Then, control computer  521  transmits the text information to a display such as display  701  so that the user can view this information. In another embodiment, voice message system  505  will automatically convert the TTY information to text before storing the message. If a user of a digital telephone such as digital telephone  513  is recovering a message stored in voice message system  505  which had not been previously determined to have TTY information, the user can actuate a button such as button  714  of  FIG. 7  to indicate to control computer  521  that this is a TTY transmission. Control computer  521  is responsive to the button actuation to request that voice message system  505  restart the message. Control computer  521  then bridges TTY controller  506  into the transmission path, mutes the transmission path to digital telephone  513 , and utilizes the display of digital telephone  513  to display the TTY message to the user as it is retrieved from voice message system  505 .  
         [0035]      FIGS. 8 and 9  illustrate, in flowchart form, an embodiment of operations performed by a control computer controlling a telecommunication system such as control computer  521 . After being started in block  801 , decision block  802  determines if the incoming call is using TTY transmissions. If the answer is yes, decision block  803  determines if the called telephone is to display the TTY incoming information on its digital display. As previously noted, the computer controlling the telecommunication operation can make this decision based on service information for the called telephone or the fact that the called telephone indicates by actuation of a button when the call is set up to the called telephone. Decision block  803  also performs the operation of the called telephone being informed that the incoming is or may be a TTY call. If the answer is no in decision block  803 , control is transferred to block  804  which processes the incoming call in a normal manner before returning control back to decision block  802 .  
         [0036]     If the answer in decision block  803  is yes, the TTY controller is enabled to translate the TTY encoded characters into the digital display format, and the switching network is set up by block  807  to transport both the audio and the digital display information to the called telephone. Finally, block  808  performs normal processing before returning control back to decision block  802 .  
         [0037]     Returning to decision block  802 , if there is not an incoming TTY call, control is transferred to decision block  809  which determines if a telephone is originating a call to a voice messaging system for a TTY message. Either the voice message system or the control computer may make the determination of a TTY message. If the answer is yes, control is transferred to decision block  811  which determines if the originating telephone has indicated in some manner that the digital display is to be used for the TTY information. If the answer is no, block  812  performs normal processing before returning control back to decision block  802 .  
         [0038]     If the answer is yes in decision block  811 , control is transfer to block  901  of  FIG. 9 . Block  901  enables the TTY controller to perform the translation between TTY protocol characters and the digital display protocol utilized for the digital display; and block  902  properly sets up the switching network. Finally, block  903  performs normal processing before returning control back to decision block  802  of  FIG. 8 .  
         [0039]     Returning to decision block  809  of  FIG. 8 , if the answer is no, control is transferred to decision block  904  of  FIG. 9 . During a normal telephone conversation i.e. one that had not been previously determined to contain TTY messages, decision block  904  determines if the telephone has indicated that it wishes to utilize the digital display for TTY information. This capability allows the user to determine at any time that it is desirable to utilize the digital display for TTY information. If the answer is yes in decision block  904 , blocks  906 - 908  perform the same operations as blocks  901 - 903 . If the answer is no in decision block  904 , control is returned back to decision block  802 .  
         [0040]     When the operations of devices  521  and  609  are implemented in software, as is shown in  FIGS. 8 and 9 , it should be noted that the software can be stored on any computer-readable medium for use by or in connection with any computer related system or method. In the context of this document, a computer-readable medium is an electronic, magnetic, optical, or other physical device or means that can contain or store a computer program for use by or in connection with a computer related system or method. Devices  521  and  609  can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “computer-readable medium” can be any means that can store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. For example, the computer-readable medium can be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM) (electronic), a read-only memory (ROM) (electronic), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory) (electronic), an optical fiber (optical), and a portable compact disc read-only memory (CDROM) (optical). Note that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured via optical scanning of the paper or other medium and then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and stored in a computer memory.  
         [0041]     In an alternative embodiment, where devices  521  and  609  are implemented in hardware, devices  521  and  609  can be implemented with any or a combination of the following technologies, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc.  
         [0042]     Of course, various changes and modifications to the illustrated embodiments described above would be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the following claims except in so far as limited by the prior art.