Chapter 9: Conversation Functionality and Controls

  • 901  General
  • 902  Real-Time Text Functionality
  • 903  Voice Mail, Messaging, Auto-Attendant, Conferencing, and Interactive Voice Response
  • 904  Information About Call Status and Functions
  • 905  Video Communication Support
  • 906  Audio Clarity for Interconnected VoIP
  • 907  Alternate Alerting for VoIP Telephone Systems

901 General

901.1 Scope.  The provisions of this chapter shall apply where required by Chapter 1, or where referenced by a requirement in this document.

Advisory 901.1 Scope.  This chapter covers ICT features that support a real time telecommunications conversation, whether it is in an audio, text, or video format.  Much of the chapter discusses conversation functionality apart from audio, which is covered in Chapter 8 (Audio Output from Hardware).

902 Real-Time Text Functionality

902.1 General.  ICT that provides real-time voice conversation functionality shall support real-time text (RTT) functionality and shall conform to 902.

902.2 Real-Time Text Interoperability.  ICT shall provide at least one system for RTT communication that conforms to 902.4.

902.3 Real-Time Text Reliability.  ICT shall provide at least one system for RTT communication that conforms to 902.3.1 through 902.3.5.

Advisory 902.3 Real-Time Text Reliability.  This provision covers hardware and software products for voice communication and video communication.

A best practice is for voice terminal hardware and software to minimize interference in order to maximize intelligibility of speech.

902.3.1 Standard RTT Format.  The RTT format shall be a standard RTT format for the voice platform that is supported by all terminals, routers, gateways, and other products on that platform.

902.3.2 RTT Transmission Delay.  The RTT system shall transmit characters with less than 1 second delay from entry when entered at 5 characters per second (cps) or less.

902.3.3 RTT System Error Rate.  The RTT system shall transmit text with less than 1% total character error rate at the peak network traffic specified for intelligible speech transmission.

Advisory 902.3.3 RTT System Error Rate.  This intent of this provision is to ensure that when the network is at its highest traffic level, text transmission, and video communication will be reliable.

902.3.3.1 Equitable Support for RTT and Video Communication.  At peak network traffic specified for intelligible speech transmission, the RTT system shall function on the network whenever speech communication and video communication are supported.

902.3.4 RTT System Speech and Text Support.  The RTT system, together with the audio system, shall support speech and text in both directions in the same call session.

902.3.4.1 Simultaneous Speech and Text.  When the call system is Internet Protocol (IP) based, the RTT system, together with the audio system, shall support speech and text simultaneously in both directions.

902.3.5 No Audio Tone Use.  The RTT system shall not use audio tones for transmission of RTT over IP.

902.4 Interoperability with Outside Systems.  When ICT interoperates outside of its closed system, or when ICT connects to other systems, ICT shall conform to 902.4.1 through 902.4.3.

902.4.1 PSTN.  When ICT interoperates with the Public Switched Telephone Network (PSTN), RTT shall use the TIA 825A Baudot standard for TTY signals at the PSTN interface.  RTT in this instance shall conform to TIA 825-A (2003) (incorporated by reference, see “Referenced Standards and Guidelines” in 255 Chapter 1 and 508 Chapter 1).

902.4.2 VoIP Using SIP.  When ICT interoperates with Voice over Internet Protocol (VoIP) products or systems using Session Initiation Protocol (SIP), they shall support transmission of RTT that conforms to a commonly used cross-manufacturer non-proprietary standard.

Advisory 902.4.2 VoIP Using SIP.  Session Initiation Protocol (SIP) is a signaling protocol for Internet conferencing, telephony, presence, events notification, and instant messaging.

902.4.3 Other Call Control System.  When ICT interoperates with other VoIP products or systems using a specific call control system other than SIP, RTT shall use a standard RTT protocol that conforms to 902.4.

Advisory 902.4.3 Other Call Control System.  All products may support and use other protocols in addition to those specified in 902.4, as long as they meet 902.4.

For the purposes of this section, a platform may be a public telecommunication platform like an Instant Messaging Service (IMS).  It also may be a proprietary telecommunication platform such as a proprietary VoIP system installed in agencies for use over the Internet (and which may or may not be connected to the public telecommunication system).

902.5 RTT Error Rate in Pass-through Products.  Firewalls, routers, gateways and other products that pass real-time voice communication shall also pass real-time text communication signals, including mixed voice and real-time text, without distortion or error beyond 1 percent.

Advisory 902.5 RTT Error Rate in Pass-through Products.  Transmitted mistakes in text may be due either to inaccuracy of information entered by users or to errors caused by RTT pass-through technology.  This provision refers to errors caused by the technology, not by the person.

902.6 Real-Time Text in Voice Terminal Hardware and Software.  Terminal hardware or software that is capable of providing voice communication in real-time shall conform to 902.6.1 or 902.6.2.

Advisory 902.6 Real-Time Text in Voice Terminal Hardware and Software.  The term “terminal” is industry standard vernacular for what end users commonly would refer to as a “telephone”.

902.6.1 RTT over IP.  Terminals that provide voice conversation over Internet Protocol (IP) in any form shall conform to 902.6.1.1 and 902.6.1.2.

902.6.1.1 RTT Capability.  Terminals having RTT send or receive capability shall conform to 902.6.1.1.1 and 902.6.1.1.2.

902.6.1.1.1 Display of RTT.  Terminals having a user interface with a multi-line display, or a user interface that runs on devices that have a multi-line display, shall display any RTT that is received in the format for the voice and RTT system being used on the network on which it is installed.

902.6.1.1.2 Text Generation.  Terminals having text generation capability shall allow users to send RTT in the format for the voice and RTT system being used on the network on which it is installed.

902.6.1.2 Connection of Alternate Device.  Terminals having neither RTT send or receive capability shall support the addition of terminals and equipment attached to the terminal that supports RTT functionality in conjunction with the voice call functionality.

902.6.2 TTY Compatibility.  Terminals that provide voice conversation which are analog or time-division multiplexing (TDM) digital wired terminals shall conform to 902.6.2.1 and 902.6.2.2.

Advisory 902.6.2 TTY Compatibility.  These requirements ensure compatibility of telephones with TTYs.  Time-division multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel.

902.6.2.1 TTY Connection.  Terminals shall support the connection of a TTY via an RJ-11 jack.

902.6.2.2 Simultaneous or Combination of Speech and Text.  Terminals covered by this requirement shall conform to 902.6.2.2.1 or 902.6.2.2.2.

Advisory 902.6.2.2 Simultaneous or Combination of Speech and Text.  This provision supports the use of both text and speech in conversations by people with hearing or speech disabilities.

Older technologies required each person on the call to take turns communicating throughout the conversation.  Advances in technology enable users with the specialized technology to converse simultaneously.  These conversations may occur directly between two parties or through use of a telecommunications relay service.  This service uses operators, called Communications Assistants, to facilitate telephone calls between people with hearing or speech disabilities and other individuals.

A person who is deaf or hard of hearing with good speech may use a technique called “voice carry over” (VCO) to talk and utilize a text terminal, such as a TTY, to read the response of the other party.  Similarly, a person with a speech disability may use a text terminal, such as a TTY, to send their communication while using a telephone to listen to a response from the other party via “hearing carry over” (HCO).

902.6.2.2.1 Simultaneous Speech and Text.  Terminals covered by this requirement shall be capable of simultaneous speech and text conversation.

902.6.2.2.2 Microphone Control.  Terminals shall provide a microphone that users are able to turn on and off to permit users to converse through any combination of speaking, listening, typing, or reading.

903 Voice Mail, Messaging, Auto-Attendant, Conferencing, and Interactive Voice Response

903.1 General.  ICT that includes voice mail, messaging, auto-attendant, conferencing, and interactive voice response (IVR) functions shall conform to 903.

Advisory 903.1 General.  The provision covers services that use voice recognition and traditional telecommunications products.

903.2 Comparable Functionality for RTT Users.  All functionality of ICT covered by this section which is available to voice users shall also be directly available to users of RTT.

Advisory 903.2 Comparable Functionality for RTT Users.  The intent of this provision is to ensure that people who are deaf are provided a comparable level of service to people who are hearing.  Historically, services provided to real-time text users have not been available in a similar quantity or quality as services provided to traditional phone users.

A best practice is for RTT broadcast messages in IP systems to be sent along with voice mail messages.  For analog systems, this is not practical.  When products do not support dedicated TTY messaging, a best practice is to offer TTY users an alternate method, such as email or website postings, for accessing RTT broadcast information.

This provision does not require automatic conversion between voice and text.

Calls made through telecommunications relay services are not direct and do not satisfy this requirement.

903.3 Message and Prompt Navigation.  ICT covered by this section shall provide controls that allow users to pause, skip, rewind, slow down, and repeat all messages and prompts.

Advisory 903.3 Message and Prompt Navigation.  An example of a prompt is an instruction to save or delete a voice mail message after a user listens to the voice mail message.

For providing features such as skip and slow down, the specifications for the Digital Talking Book ANSI/NISO Z39.86-2002 standard can be used as a reference.

903.4 Audio Encoder Intelligibility.  ICT covered by this section shall use an audio encoder that complies with the ITU-T G.722 standard for encoding and storing audio information (1988) (incorporated by reference, see “Referenced Standards and Guidelines” in 508 Chapter 1 and 255 Chapter 1).

Advisory 903.4 Audio Encoder Intelligibility.  G.722 is an ITU standard coder-decoder program that provides 7 kHz wideband audio at data rates from 48, 56, and 64 kbits/s.  This standard offers a significant improvement in speech quality over earlier standards, and thus provides greater accessibility to users.

903.5 No Background Sounds.  ICT covered by this section shall provide prompts that do not have any background sounds.

Advisory 903.5 No Background Sounds.  The purpose of this provision is to maximize intelligibility of prompts for people with hearing disabilities.

904 Information About Call Status and Functions

904.1 General.  Information in an electronic format provided by an interface of ICT that supports two-way conversation shall conform to 904.

Advisory 904.1 General.  An example of information in an electronic format provided by an interface of ICT that supports two-way conversation is the display on a telephone.

904.2 Call Status and Product Functions.  Information provided about call status and related product functions shall conform to Chapter 5 (Electronic Documents).

Advisory 904.2 Call Status and Product Functions.  Types of information provided about call status addressed by this requirement include caller identification, messages waiting, duration of call in progress, dialing directory, wireless signal strength, and battery power.

Related product functions include search and set-up.

Products can often meet this provision through redundancy.  An example of redundancy is using both a stutter tone and a blinking LED to indicate the presence of a new message.

A best practice is for telephone systems to send information to a connected computer.  This practice promotes accessibility of information because people can use their preferred assistive technology.  For example, a person with low vision can use screen magnification to provide enlargement.

905 Video Communication Support

905.1 General.  ICT that is used for video communication in real-time between and among individuals shall support interoperability that permits video communication between and among users of terminals from different manufacturers and service providers, and shall conform to 905.

905.2 Audio Output and Input.  ICT covered by 905.1 shall be equipped with a speaker or with an audio jack and a microphone capable of being muted.

Advisory 905.2 Audio Output and Input.  The purpose of this provision is to support simultaneous audio and visual conversations.

It should be possible to use products or systems in any combination of speaking, listening, signing, or viewing.  An example is a person who is deaf who prefers to speak when using video communication with a hearing person who is signing.

905.3 Video Communication Quality.  ICT covered by 905.1 shall conform to 905.3.1 through 905.3.2.

Advisory 905.3 Video Communication Quality.  The purpose of this provision is to ensure that products or systems that are used to transmit video conversations provide sufficient quality and fluidity for real-time video conversation in which at least one party is using a visual method of communication, such as sign language.

Communication products or systems that are used to transmit video conversation can facilitate lip reading and finger-spelling, as well as support sign language conversation.

The separate requirements for speed, data stream, and latency are needed to provide sufficient quality and fluency that will support real time video communication where one or more parties are using sign language or taking in the picture.

905.3.1 Video Communication Data Processing.  ICT supported by 905.1 shall conform to 905.3.1.1 through 905.3.1.3.

905.3.1.1 Speed.  ICT covered by 905.1 shall support a speed of 30 frames per second (FPS).

905.3.1.2 Data Stream.  ICT covered by 905.1 shall be capable of sustaining a full-duplex synchronous data stream of 256 kbps simultaneously and symmetrically for both inbound and outbound data.

Advisory 905.3.1.2 Data Stream.  Sign language requires continuous and smooth video connection to support communication because sign language includes hand movements and facial expressions that are visually nuanced.

Data connections that are established at a rate lower than 256 kbps often result in missing or stuttering images or freeze frames.  This result impedes the utility of the video for individuals using sign language communication.

905.3.1.3 Latency.  ICT covered by 905.1 shall have a latency of less than 400 milliseconds.

905.3.2 Video Display Quality.  ICT covered by 905.1 shall conform to either 905.3.2.1 and 905.3.2.2, or 905.3.2.3.

905.3.2.1 Display Screen Resolution.  ICT covered by 905.1 shall support a display with a minimum resolution equal to Common Intermediate Format (CIF) resolution (352 x 288 pixels) (incorporated by reference, see “Referenced Standards and Guidelines” in 508 Chapter 1 and 255 Chapter 1). 

905.3.2.2 Display Connectors.  ICT covered by 905.1 shall have standard connectors conformant with 703, and the connectors shall be capable of supporting a device with a resolution of 640 x 480 pixels.

905.3.2.3 Alternative Video Display.  Where ICT covered by 905.1 does not conform to 905.3.2.1 and 905.3.2.2, then an alternate video display screen shall be provided and it shall conform to 905.3.2.3.1 through 905.3.2.3.3.

905.3.2.3.1 Alternate Display Screen.  When an alternate display screen is provided, at least one model shall have at least a 15 inch screen with video output in an industry standard non-proprietary format supporting a minimum color display resolution of 640 x 480 pixels.

Advisory 905.3.2.3.1 Alternate Display Screen.  Examples of industry standard non-proprietary formats for video output include National Television System Committee (NTSC), VGA, and DVI.

905.3.2.3.2 Alternate Display Connectors.  An alternate display screen provided under this section shall have standard connectors conformant with 703.

905.3.2.3.3 Common Technologies.  An alternate display screen provided under this section shall be supported by the same technology as the primary product.

Advisory 905.3.2.3.3 Common Technologies.  Products that provide conversation functionality use a variety of communications technologies and infrastructure.  Where an alternative display screen is provided as a means to meet this requirement, the alternative must be supported by technologies similar to the primary product and must be readily available and supported in the same market.  For example, a PAL (Phase encoding line — a type of television encoding system) compliant alternative product would not meet this requirement where the primary device is sold in the U.S., even though the same 3G frequencies are (infrastructure) used in other PAL markets, since the U.S. uses the NTSC standard, not PAL.

905.4 Non-Auditory Alerting System.  ICT shall provide a non-auditory alerting system for incoming video communications that conforms to either 905.4.1 or 905.4.2.

905.4.1 Built-in.  ICT shall include a built-in non-auditory alerting system.

905.4.2 External Compatibility.  ICT shall provide compatibility with an external non-auditory alerting system.

905.5 Visual Indicator of Camera Status.  ICT shall provide a visual indication of whether the camera is on or off.

Advisory 905.5 Visual Indicator of Camera Status.  This requirement supports 302 because security policy may not permit use of video communication products or systems unless the on/off status of the camera can be visually determined.

905.6 User Controls.  When ICT provides user controls, privacy features that include audio and video on and off shall be provided.

905.6.1 Location.  User controls for video on and off shall be provided in the same location as user controls for audio on and off.

906 Audio Clarity for Interconnected VoIP

906.1 General.  ICT that is interconnected VoIP telephones and interconnected VoIP telephone-emulation software shall conform to 906.

Advisory 906.1 General.  The intent of this provision is to ensure audio clarity for VoIP calls.

906.2 ITU Standard G.722.  ICT shall transmit and receive speech that is digitally encoded in the manner specified by International Telecommunication Union (ITU) Standard G.722 for encoding and storing audio information (1988) (incorporated by reference, see “Referenced Standards and Guidelines” in 508 Chapter 1 and 255 Chapter 1).

Exception:  Where ICT is a closed system, standards other than ITU Standard G.722 may be used, so long as equivalent or better acoustic performance is provided, and if conversion to International Telecommunication Union (ITU) Standard G.722 at the borders of the closed system is supported.

Advisory 906.2 ITU Standard G.722 Exception.  An example of a closed system is a telephone network system on a Federal site that enables calls to be placed between buildings and departments within that site, but is not used to receive or make calls outside of that site system.

907 Alternate Alerting for VoIP Telephone Systems

907.1 General.  ICT that is interconnected VoIP telephone systems, interconnected VoIP terminal adapters, or software for interconnected VoIP telephone systems shall conform to 907.

907.2 Alternate Alerting System.  For incoming communications, ICT shall provide an alternate alerting system conforming to either 907.2.1 or 907.2.2.

Advisory 907.2 Alternate Alerting System.  The intent of this provision is to provide people who are deaf and hard of hearing with accessible alerting systems for incoming communications.

An alternate alerting system can be visual, tactile, or loud audible.

907.2.1 Built-in.  ICT shall include a built-in alternate alerting system.

Advisory 907.2.1 Built-in.  Small built-in light emitting diodes (LEDs) are insufficient to alert people with hearing disabilities to incoming calls if the person is not looking directly at the device.  Large visual alerts combined with loud audible alerts are more effective.

907.2.2 External Compatibility.  ICT shall provide a mode of operation that electronically signals an external alternate alerting system.

Advisory 907.2.2 External Compatibility.  Examples of external alerting devices include:  loud ringers, light flashers, and vibrating devices.

An external alternate alerting system which features a microphone that is placed near a sound source, such as a telephone, does not conform to 907.2.2 because the ICT does not provide a mode of operation that electronically signals the alternate alerting device.