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TIA TIA/EIA/IS-840-A

Minimum Performance Standards for Text Telephone Signal Detector and Text Telephone Signal Regenerator - Revision of TIA/EIA/IS-840

Organization:
TIA - Telecommunications Industry Association
Year: 2001

Abstract: Introduction
Text telephones enable persons with hearing issues to communicate over conventional telephone lines, using written text messages. There are two types of text telephones: TTY (Tele TYpe) and TDD (Telecommunications Device for the Deaf). TTYs are basically mechanical teleprinters and TDDs are their electronic counterparts. In this document, the term "Text Telephone" refers to TTY, TDD, or both devices. Virtually all text telephones support "5-bit operational mode" using Baudot code. In this operational mode, the communication channel is half-duplex with no channel turnaround. The modulation is frequency shift-keyed (FSK) without carrier. This FSK uses 1400 Hz for a binary 1 and 1800 Hz for a binary O. A bit duration of either 20 or 22 ms (k0.4 ms) is used, providing a nominal data signaling rate of either 50 or 45.45 bits per second or baud, respectively. The bit duration of 22 ms is used in the United States. Each character consists of 5-bit sequence preceded by one start bit at the frequency of 1800 Hz and followed by a minimum of one stop bit at 1400 Hz. There are two shift codes: letters sequence (11111) and figures sequence (11O11).
Passing the Baudot tones through the present TIA/EIA-136 digital mobile systems results in strongly distorted received tones. Telecommunication Industry Association (TIA) has coordinated the efforts to find a favorable solution to improve the TTY/TDD signaling in TIA/EIA- 136 digital wireless system. This document is to accompany the extension to TIA/EIA- 136-410 TDMA Enhanced Full-Rate Voice Codec (hereafter referred to as the text telephone extension) to improve the TIA/EIA- 136 digital wireless system's performance for text telephone signals. The text telephone extension consists of text telephone signal detector, speech/text telephone signal encoder (modified TIA/EIA- 136-4 1 O encoder), speech/text telephone signal decoder (modified TIA/EIA-136-4 1 O decoder), and the text telephone signal regenerator. The speech/text telephone signal encoder and decoder are modified versions of TIA/EIA- 136-4 1 O encoder and decoder respectively. In this document the term detector refers to text telephone signal detector and the term regenerator refers to text telephone signal regenerator. The speech/text telephone signal encoder and decoder, as shown in Figure 4, shall be implemented as specified in IS-813-L4. Hereafter, the term encoder is used for speech/text telephone signal encoder and the term decoder is used for referring to speech/text telephone signal decoder. In this document the term detector refers to text telephone signal detector. However, the detector and the regenerator need not be implemented in bit-exact manner. This document describes the minimum performance requirements for the detector and the regenerator. Annex A of this document describes test input vectors and reference output vectors for the detector and the regenerator. All detectors and the regenerators used for implementation of text telephone I extension of TIA/EIA-136-41O vocoder shall meet the minimum performance requirements specified in this document. Section 2 gives a brief description of the text telephone extension of TIA/EIA-136-41O vocoder. Section 3 specifies the test resources and utilities needed. Section 4 describes the test procedure for verifying minimum performance requirements for the detector. Section 5 describes the minimum performance requirnts for the detector. Section 6 describes the test procedure for verifying minimum performance requirements for the regenerator. Section 7 specifies the minimum performance requirements for the regenerator. Section 8 describes the test procedure for testing tandem operation and degraded channel performance. Section 9 describes the performance requirements for tandem operation. Section 1O describes the performance requirements for various degraded channel conditions. Annex A describes the test vectors to be used for testing various performance requirements for text telephone extension.
URI: http://yse.yabesh.ir/std;query=autho47037D83FCDC49A961598F1EFDEC9FCD/handle/yse/164426
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contributor authorTIA - Telecommunications Industry Association
date accessioned2017-09-04T17:41:23Z
date available2017-09-04T17:41:23Z
date copyright09/01/2001
date issued2001
identifier otherDXWQSAAAAAAAAAAA.pdf
identifier urihttp://yse.yabesh.ir/std;query=autho47037D83FCDC49A961598F1EFDEC9FCD/handle/yse/164426
description abstractIntroduction
Text telephones enable persons with hearing issues to communicate over conventional telephone lines, using written text messages. There are two types of text telephones: TTY (Tele TYpe) and TDD (Telecommunications Device for the Deaf). TTYs are basically mechanical teleprinters and TDDs are their electronic counterparts. In this document, the term "Text Telephone" refers to TTY, TDD, or both devices. Virtually all text telephones support "5-bit operational mode" using Baudot code. In this operational mode, the communication channel is half-duplex with no channel turnaround. The modulation is frequency shift-keyed (FSK) without carrier. This FSK uses 1400 Hz for a binary 1 and 1800 Hz for a binary O. A bit duration of either 20 or 22 ms (k0.4 ms) is used, providing a nominal data signaling rate of either 50 or 45.45 bits per second or baud, respectively. The bit duration of 22 ms is used in the United States. Each character consists of 5-bit sequence preceded by one start bit at the frequency of 1800 Hz and followed by a minimum of one stop bit at 1400 Hz. There are two shift codes: letters sequence (11111) and figures sequence (11O11).
Passing the Baudot tones through the present TIA/EIA-136 digital mobile systems results in strongly distorted received tones. Telecommunication Industry Association (TIA) has coordinated the efforts to find a favorable solution to improve the TTY/TDD signaling in TIA/EIA- 136 digital wireless system. This document is to accompany the extension to TIA/EIA- 136-410 TDMA Enhanced Full-Rate Voice Codec (hereafter referred to as the text telephone extension) to improve the TIA/EIA- 136 digital wireless system's performance for text telephone signals. The text telephone extension consists of text telephone signal detector, speech/text telephone signal encoder (modified TIA/EIA- 136-4 1 O encoder), speech/text telephone signal decoder (modified TIA/EIA-136-4 1 O decoder), and the text telephone signal regenerator. The speech/text telephone signal encoder and decoder are modified versions of TIA/EIA- 136-4 1 O encoder and decoder respectively. In this document the term detector refers to text telephone signal detector and the term regenerator refers to text telephone signal regenerator. The speech/text telephone signal encoder and decoder, as shown in Figure 4, shall be implemented as specified in IS-813-L4. Hereafter, the term encoder is used for speech/text telephone signal encoder and the term decoder is used for referring to speech/text telephone signal decoder. In this document the term detector refers to text telephone signal detector. However, the detector and the regenerator need not be implemented in bit-exact manner. This document describes the minimum performance requirements for the detector and the regenerator. Annex A of this document describes test input vectors and reference output vectors for the detector and the regenerator. All detectors and the regenerators used for implementation of text telephone I extension of TIA/EIA-136-41O vocoder shall meet the minimum performance requirements specified in this document. Section 2 gives a brief description of the text telephone extension of TIA/EIA-136-41O vocoder. Section 3 specifies the test resources and utilities needed. Section 4 describes the test procedure for verifying minimum performance requirements for the detector. Section 5 describes the minimum performance requirnts for the detector. Section 6 describes the test procedure for verifying minimum performance requirements for the regenerator. Section 7 specifies the minimum performance requirements for the regenerator. Section 8 describes the test procedure for testing tandem operation and degraded channel performance. Section 9 describes the performance requirements for tandem operation. Section 1O describes the performance requirements for various degraded channel conditions. Annex A describes the test vectors to be used for testing various performance requirements for text telephone extension.
languageEnglish
titleTIA TIA/EIA/IS-840-Anum
titleMinimum Performance Standards for Text Telephone Signal Detector and Text Telephone Signal Regenerator - Revision of TIA/EIA/IS-840en
typestandard
page34
statusActive
treeTIA - Telecommunications Industry Association:;2001
contenttypefulltext
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