438 12 Accessible Information: An Overview

Figure 12.24. Big Button 100 telephone (photograph reproduced by kind permission of British Telecommunications plc, UK)

accessibility guidelines and then reports on the accessibility of each webpage. It can integrate with HTML editors to facilitate the fixing of identified problems. Sites that pass the test can display the Bobby Approval logo on the site, the head and helmet of a U.K. police officer or ‘bobby’.

12.8 Telecommunications

Although the functions of speaking and listening on the telephone do not require vision, dialling a number does. The additional telephone functions that are now available, such as caller identification and sending text messages, also require vision. Therefore, these functions need to be made accessible to blind and visually impaired people. For dialling, the simplest solution is to have large keys with very clear contrast characters and a small bump to mark the number 5, as shown in Figure 12.24, though this is more practicable for landlines than the small handsets of mobile phones. There are also voice dialling and talking caller identification systems. Screen readers for mobile and landline phones have been developed.

12.8.1 Voice Dialling General Principles

Voice dialling allows the user to dial a number by speaking it or the name of the person being called. There are two types, speaker dependent and speaker independent. In speaker dependent systems the telephone will only respond to recorded names, and generally only when spoken by the person who recorded them initially. Therefore, each name must be spoken and recorded one to three times first before it can be dialled. The maximum number of voice dial entries is generally limited. Speaker independent voice recognition does not require prerecording and the name can be spoken by anyone. The system will automatically match the spoken name with the closest name in the telephone book. Speaker dependent voice dialling is more common, particularly on older telephones.

Speaker independent voice recognition systems are required to connect a single word to a number in the phone book. This involves sampling an analog speech signal and detecting the start and end-points of the word. The three most commonly used algorithms are threshold detection, zero-crossing (that is, the number of times the signal amplitude crosses the axis) and zero-crossing with a threshold, which is preferred in noisy environments. Zero-crossing rates are generally higher in speech sequences than in noise and speech generally has higher magnitudes. The noisy speech signal is filtered through a FIR filter to improve the signal-to-noise ratio. The recorded sequence starts before the start of the word to give information on the noise that can be used in the construction of the filter. The speech signal is blocked into frames and the coefficients are extracted from each frame and quantized. Either matched filters or the Hidden Markov Model can be used to detect what labels correspond to the spoken word.

12.8.1.1 Voice Dialling Systems

There are a number of different voice dialling systems, some of which have additional features, such as screenreading, and are generally correspondingly expensive. Some dialling systems can be used with any telephone, whereas others are designed for a specific series of telephones. OnStar Personal Calling provides voice dialling features. The user is able to place calls or store telephone numbers by saying ‘dial’ or ‘store’ respectively and then saying the whole number without pauses. The system then repeats the number to check whether it is correct.

The Dialtalk Pocket Telephone Dialler (see Figure 12.25) from Cobolt Systems speaks each digit as it is entered and allows the user to erase and correct each digit. Pressing the ‘speak’ button reads back the whole number. The tones can then be transmitted to the telephone to dial the number by holding the Dialtalk close to the mouthpiece and pressing ‘dial’. The Dialtalk has ten memories, adjustable volume and last number redial. It can be used with tone or pulse telephones that are connected to a tone exchange. Each memory can hold 15 digits and memories can be combined for dialling very long numbers. The Handsfree Freedom Voice Dialer dials numbers that have been stored by the user speaking the person’s name. It can store a maximum of 50 names. The Infinity Voice Dialer will also dial a number spoken by the user that has not been programmed into the dialler. It has a maximum of 40 spoken names or numbers. In both cases the programmed phone numbers can be up to 35 digits long. Voice prompts are given for recording and deleting names and numbers. The system is speaker dependent and trained to hear a particular voice, giving better speech recognition. It works with all standard telephones; include cordless ones, as long as they are touch tone. The Voice dialler is installed between the telephone and wall jack, similarly to an ansaphone. The system may not work on business telephone systems which have their own internal wiring systems.

The Voice Activated Speaker Phone has no handset. When the telephone rings and the user says ‘hello’, the telephone is answered and the conversation takes place over a speaker phone. The call can be ended by pressing the ‘off ’ button on the keypad or using the wireless remote. Compusult’s TeleTalk (see Figure 12.26)

440 12 Accessible Information: An Overview

Figure 12.25. Dialtalk pocket telephone dialler (photograph reproduced by kind courtesy of Cobolt Systems Ltd., UK)

Figure 12.26. Teletalk (photograph reproduced by kind courtesy of Compusult Ltd., Canada)

provides access to the telephone console indicator and message display information for blind and visually impaired people. The system captures call related data and converts it to both speech and output on a large high contrast display. There are different TeleTalk systems for different models of telephone. There are several different configurations, based on different combinations of electronics hardware, software and computers.

Caredec Products distributes a number of talking telephone products. TALKS 80 is a screen reader for the Nokia Communicators 9x series of phones. It enables the user to write and read text messages, e-mail and text documents, dial a number from the telephone book, add entries to and edit the contact data base. It also provides an appointment calendar, a calculator and an alarm clock. Talks 60 provides similar functions for the Symbian Series 60 phones. Both products use ETI Eloquence text-to-speech software.

12.8.2 Talking Caller ID

Talking caller identification systems give blind and visually impaired people the number and, in some systems, also the name of the caller, with a database to store names and numbers. Some systems have additional features such as being able to send customised messages to particular callers, notifying the user by email that they have received a call and refusing calls from particular numbers. Most of the systems require the user to subscribe to a caller ID service.

Cobolt Systems’s talking caller ID allows the user to record a message, typically the caller’s name so that future incoming calls from the same person will lead to the message being spoken. The message features can be used with up to 20 different numbers. The speaker volume is adjustable. Users need to subscribe to the BT/Cable caller display service. An incoming call log displays up to 99 calls, with the time, date, number and name (if stored in the directory), but only announces the calls that have been assigned a name or other message. Assistance from a sighted person may be required in setting up the caller ID. The fact that only some calls are announced and that the device cannot necessarily be set up independently are minor disadvantages.

Talking Caller ID is a US shareware program that informs the user who is calling before they pick up the telephone. It requires users to subscribe to a telephone company caller id service and have a caller id capable modem or caller id computer hardware device. Talking Caller ID can work with both name and number or number alone services. It stores details of every person who has called, with their name, telephone number and the date, time and number of rings, as well as any custom greeting or photo, in a database. The program can look up the names in the database, allowing users with number only caller id services to see and hear the name of the caller. A recorded custom greeting in the user’s voice, photo or text file can be spoken or displayed whenever a call from a particular caller is received. Installing a free speech recognition engine enables the program to support speech recognition, including training for higher accuracy for the user’s voice.

Call blocking by number or name can be used to screen out unwanted calls, with a database to which details of unwanted callers can be added. When calls are received from unwanted callers, the modem picks up the line and hangs up and the program informs the user that the call was blocked and states who was trying to call. The e-mail notification feature can send an e-mail to any Internet mail address when a call is received. The program also has an ansaphone feature with customisable outgoing messages. The Remote Control for Talking Caller ID is an add-on that allows users to receive caller id information from their computer from any touch tone phone. The computer reads back the information requested through a speech engine. The program can be used in the UK, but requires appropriate hardware. The option Caller ID Plug provides an audio alert whenever the user receives new voice mail. There is also the option to send a notifying message to the user’s pager or e-mail when voice mail is received.

Panasonic produce several cordless phones with Talking Caller ID and which incorporate text-to-speech programs. A Caller ID service is required.