Many people have asked me (Karen) if it's possible to connect to their friend's TTY using their PC and modem. The general answer is: NO. There is no software package that will magically transform your normal modem into a TTY-modem, but that's what this V.18 standard is all about -- making sure future generations of modems will support TTY encoding. But no software package can turn a generic modem into a TTY modem, you *MUST* buy a TTY-modem.
Several companies will sell you a TTY modem and if you have an IBM PC Windows compatible machine, there are some nice TTY-modem answering machine terminal programs available that will turn your TTY-modem into an answering machine and high powered TTY terminal. Very nice. Contact Harris Communications or one of the other vendors on my vendor's page for more information.
It is rumored that some of the new v.34 (28.8Kbps) modems from Motorola and other companies will have V.18 (tty) support. So far, it just seems a rumor, but we should apply pressure on these companies to accomodate Deaf/HOH/Speech Imparired people.
"It's not only good business... it's the law.--- Karen Nakamura, October 27, 1995
Click to go back up to Karen Nakamura's Deaf Resources.acesses since August 8, 1995.
******************************************************** ** THERE ARE TWO PARTS: IMPLICATIONS & RECOMMENDATION ** ******************************************************** ************************************************** What are the implications of v.18? v.18 is the first telecommunication standard that has recognized the technological ghettoization of TTY users. It is a breakthrough to have a standards group address this issue, and a first step toward universal design for accessibility of telecommunication products. It will spawn new products, both in the modem and TTY markets. However, v.18 is not a requirement that all new modems be TTY-compatible. It is a "reference" standard that tells industry how to achieve compatibility. In the U.S., standards are voluntary. We are hopeful, however, that modem manufacturers will want to improve the marketability of their modems, here and in Europe, by including TTY compatibility. For example, government purchasers of modems may require v.18, as a way of enhancing their compliance with the Americans with Disabilities Act. Telephone Relay Services and 911 centers will benefit from v.18 modems. And businesses that are purchasing modems will see v.18 as a way to get a TTY for ADA compliance. v.18, if implemented in U.S. modems, will first appear in high-end, high-speed modems. Specifically, v.18 would be expected to appear in new v.34 modems. Lower-speed modems, which are typically not the focus of new design and development, will probably not carry v.18. Modem manufacturers that include v.18 will mark their products as such. This means that a buyer can check a modem's box to determine whether TTY compatibility is built- in. If v.18 is successful for allowing communication with a wide variety of TTYs, it should generate a new type of TTY (as well as computer modem) that can handle international calls. It's important to note that v.18 has yet to be tested with real-world products. There will probably be bugs to be ironed out. Gallaudet hopes to take an active role in testing and cooperating with European centers testing v.18. ************************************************** Recommendation v.18 Final Version - Sept 20, 1994 Operational and interworking requirements for modems operating in the text telephone mode Background The ITU-T, considering (a) that text telephones place special operational needs on the use of modems. (b) that for historical reasons, many existing text telephones do not use V-series modulation. (c) there is a desire to have all future GSTN text telephones employ V-series modulation. (d) to provide a migration path from the diverse installed base it will be necessary to provide interworking with existing text telephones (e) to provide for interworking the DCE will need to convert the 5-bit character code or Recommendation Q.23 (DTMF) character set used by some existing text telephones into the 7-bit code set as given in Recommendation T.50. (f) that such character conversion in the DCE be undertaken solely to enable interworking with existing text telephones and to impose no constraints on character sets used in future text telephones. recommends the procedure below. 1 Scope This Recommendation defines features to be incorporated in modems intended for use in, or communicating with, text telephones primarily used by the deaf or hard of hearing. It is the goal of this Recommendation to provide a platform on which a future universal text telephone could be built. To accommodate this procedures for interworking with most existing text telephones are provided in this Recommendation. To provide for maximum flexibility it is envisaged that text telephone mode of operation will be invoked on an as required basis in response to commands issued by the DTE. It provides for: Calling identification signals using the procedures specified in Recommendation V.8 No disconnection on loss of carrier Procedures for interoperation with: (1) Existing text telephones using a 5-bit code (2) Existing text telephones that use V. series modulation modes, (3) Existing DTMF-based text telephones, and (4) Existing European Deaf Telephone (EDT) text telephones, and (5)Others as identified 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other referenced Standards are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent editions of the Recommendations and other references listed below. A list of currently valid ITU-T Recommendations is regularly published.. - ITU-T(CCITT) Recommendation Q.23: 1988, Technical features of push-button telephone sets. - ITU-T(CCITT) Recommendation T.50: 1992, International Reference Alphabet (IRA)(Formerly International Alphabet No. 5 or IA5) - Information technology - 7-bit coded character set for information interchange - ITU-T(CCITT) Recommendation V.21: 1988, 300 bits per second duplex modem standardized for use in the general switched telephone network. - ITU-T(CCITT) Recommendation V.23: 1988, 600/1200 bits per second modem standardized for use in the general switched telephone network. - ITU-T(CCITT) Recommendation V.8 1994, Procedures for starting sessions of data transmission over the general switched telephone network. 3 Definitions For the purposes of this Recommendation the following definitions apply. CI A signal transmitted from the call DCE to indicate the general communications function, consisting of a repetitive sequence of bits at 300 bit/s, modulating Recommendation V.21(1), the low-band channel defined in Recommendation V.21. The cadence of this signal when used in this Recommendation shall be bursts of 4 CI sequences separated by 2 seconds of silence. The CI sequence when used with this Recommendation shall be coded in octets as defined in Tables 1, 2 and 3/V.8. CI shall be coded to indicate the function 'text telephone'. The 30-bit CI sequence in left-to-right order of transmission is given by: (1 1111 1111 1) (0) 0000 0000 (1) (0) 1000 0010 (1) where brackets enclose start and stop bits. TXP A signal transmitted to allow early termination of answer tone, and also to confirm V.18 capability. It consists of a repetitive sequence of bits at 300 bit/s modulating V.21(1) if transmitted from the call DCE, or modulating V.21(2) if transmitted from the answer DCE. The 40-bit TXP sequence in left-to-right order of transmission is given by: (1 1111 1111 1) (0) 0010 1011 (1) (0) 0001 1011 (1) (0) 0000 1010 (1) where brackets enclose start and stop bits. 4 Operational requirements 4.1 To allow for easy movement between data and voice modes the modem shall not initiate a disconnect. 4.2 To facilitate transfers, on a established connection, between text telephones using different modes of operation (i.e., 5-bit, T.50 CODE, DTMF), the modem shall have the capability to be configured by the user such that whenever transmission has ceased for 2 s (e.g. a call transfer) the modem shall re-assume the initial interworking state, re-initiate the calling id signal and activate the appropriate detectors (see Section 5 ). 4.3 The modem shall implement the CI signal coded as specified in Recommendation V.8 for text telephones. 4.4 The modem shall provide call progress indications to the DTE. These signals shall include, but not be limited to: BUSY, RINGING, CARRIER, LOSS OF CARRIER and CONNECT(x) where x indicates the mode of connection (e.g., V.18, EDT, etc.) 4.5 The modem shall implement Circuit 135 Received energy present (or its equivalent). Because of the subjective nature of this indication the operational thresholds of this circuit are left to the discretion of the implementors. To prevent confusion with call progress tones during call establishment, the modem shall provide filtering of the signals specified in Recommendation V.8 to the detector associated with this circuit. 5 Interworking This section provides procedures for interworking with equipment operating in accordance with Recommendations V.18, V.21, V.23, EDT, 5 - bit or DTMF based text telephones. Although it is envisaged that for most connections the user will have a priori knowledge of the type of terminal being called and will preset the modem to the correct mode, automatic procedures are provided for both originating and answering. These procedures provided for automoding and, where required for interworking modulation and protocol conversion. 5.1 Automoding Originating These procedures are based on the assumption that the modem has been placed in the V.18 mode with the CI specified in V.8 for text telephones and the called party is known to be equipped with a text telephone. The procedure is defined below, and represented in Figure 1/V.18 5.1.1 After connecting to line and dialing the number, the modem shall transmit no signal for 1 second, and then transmit the CI signal as specified in V.8 for text telephones with the ON/OFF cadence defined in §3. Detection of incoming signals shall take place during OFF periods in the signal CI, as indicated in Figure 1/V.18. After transmitting 4 of the CI sequences defined in Recommendation V.8 for text telephones (see §3), the modem shall condition its receivers to detect the following signals during the 2-second OFF period in signal CI (see Figure 1/V.18): TXP 2100 Hz (ANS) 2225 Hz 1300 Hz 1650/1850 Hz 1400/1800 Hz DTMF tones 980/1180 Hz(note) 390 Hz Note: care should be taken in the design of 980/1180 Hz detectors to prevent incorrect triggering by echoes of transmitted CI signals. If any of the above are detected the modem shall stop transmitting CI. No disconnect timers shall be started. 5.1.2 If ANS is detected the modem shall stop transmitting the CI signal, transmit no signal for 0.5 seconds, and then initiate the transmission of signal TXP in V.21(1) mode. The modem shall then monitor for 1650/1850 Hz, 1300 Hz and 390 Hz. 126.96.36.199 When the modem detects the absence of ANS, it shall stop transmission of signal TXP after completion of the current TXP sequence and continue to monitor for 1650/1850 Hz, 1300 and 390 Hz. 188.8.131.52. If the modem detects TXP it shall connect as V.18, i.e. Recommendation V.21 with the operational characteristics given in section 3. 184.108.40.206 If the modem detects 1650/1850 Hz for 0.2 second it shall connect as per Recommendation V.21. 220.127.116.11 If the modem detects 1300/2100 Hz for 1 second it shall connect as per Recommendation V.23. If 390 Hz is detected for 1 second, then the modem shall connect as per Recommendation V.23 reverse mode (i.e. transmit on the higher speed channel). 5.1.3 If the modem detects 2225 Hz it shall connect as Annex D. 5.1.4 If 1650/1850 Hz for 0.2 second, are detected the modem shall connect as per Recommendation V.21. 5.1.5 If 1300 Hz is detected for 1 second the modem connect as per Recommendation V.23. 5.1.6 If a sequence of 1400 Hz and 1800 Hz FSK signals (i.e. valid 5-bit characters)are detected the modem shall connect in the 5-bit mode using the character conversion specified in Section 5.2 and the operational characteristics specified in Annex A. 5.1.7 If Dual Tone Multi-Frequency (DTMF) signals are detected the modem shall connect in the DTMF mode using the character conversion specified in Section 5.4 and the operational characteristics specified in Annex B. 5.1.8 If 980 /1180 Hz signals are detected the modem shall start a 2 sec timer Tr and attempt to determine the data signalling rate of the sequence. 18.104.22.168 If the data signalling rate is 110 bit/s the modem shall connect in the EDT mode using the operational characteristics specified in Annex C. 22.214.171.124 If the timer expires the modem shall return to the monitor A state. 5.2 Automoding Answering 5.2.1 When in the automatic answer mode the modem shall answer the incoming call, and condition its receiver to detect : 390/450 Hz 1300 Hz 1400/1800 Hz DTMF tones 980/1180 Hz signal CI 2100 Hz 1070/1270 Hz The 3s timer Ta shall be started. No disconnect timers shall be started. The procedures are defined below, and represented in Figure 2a and Figure 2b/V.18. The order of the procedures given below, following the detection period for CI, is given for illustration only as the automoding should be ordered by the user on the basis of a "most likely to occur" scenario. (see Appendix 1) 5.2.2 If signal CI coded for text telephone is detected, the modem shall transmit answer tone ANS as defined in Recommendation V.25, and monitor for signal TXP. 126.96.36.199 If signal TXP is detected, the modem shall transmit no signal for 75±5ms, transmit 3 TXP sequences in V.21(2) mode, and then proceed as V.18 (i.e., Recommendation V.21 with the operational requirements specified in Section 4 of this Recommendation). 5.2.3 If 2100 Hz is detected the modem shall continue to monitor for 980 Hz, 1300 Hz or 1650 Hz. 188.8.131.52 If 980 Hz is detected the modem shall connect as per Recommendation V.21. 184.108.40.206 If 1300 Hz is detected the modem shall connect as per Recommendation V.23. 220.127.116.11 If 1650 Hz is detected the modem shall connect as per Recommendation V.21 reversed (in the calling mode). 5.2.4 If 980 Hz is detected the modem shall start 2.7s timer Te and monitor for 1650 Hz and 1180 Hz. 18.104.22.168 If 1650 Hz is detected the modem shall connect as per Recommendation V.21 reversed (in the calling mode). 22.214.171.124 If 1s of no signal is detected the modem shall connect as per Annex C. 126.96.36.199 If either 1180 Hz is detected or timer Te expires, the modem shall start 1 sec timer Tr and attempt to determine the data signalling rate of the data sequence. 188.8.131.52.1 If the data signalling rate is 110 bit/s the modem shall connect in the EDT mode using the operational characteristics specified in Annex C 184.108.40.206.2 If the data signalling rate is 300 bit/s or timer Tr expires the modem shall continue as per Recommendation V.21. 5.2.5 If a sequence of 1400 /1800 Hz FSK signals (i.e. valid 5-bit characters) are detected the modem shall connect in the 5-bit mode using the character conversion specified in Section 5.3 and the operational characteristics specified in Annex A. 5.2.6 If Dual Tone Multi-Frequency (DTMF) signals are detected the modem shall connect in the DTMF mode using the character conversion specified in Section 5.4 and the operational characteristics specified in Annex B. 5.2.7 If 1070/1270 Hz is detected the modem shall connect as per Annex D. 5.2.8 If Ta expires the modem shall proceed either per § 220.127.116.11 or per § 18.104.22.168. depending on the most likely scenario determined by the user. 22.214.171.124 The modem shall transmit the buffered message and start variable Timer Tm (default 3 sec) to allow for a response from the caller. If Tm expires and no response is received the modem shall proceed to next appropriate probe (e.g., ANS, carrier, or the next carrierless mode). Note: The modem shall have a stored, user changeable, default answer message (e.g. Hello, GA). Although the primary use of this stored message is to stimulate a response from a carrierless text telephone it may also be optionally sent after a connection is established with a continuos carrier based text telephone. 126.96.36.199 The modem shall transmit ANS, set 2 sec timer Tb and monitor the line for 980 Hz, 1270 Hz and 1300 Hz. 188.8.131.52.1 If 980 Hz is detected the modem shall connect as V.21 184.108.40.206.2 If 1270 Hz is detected the modem shall connect as Annex D. 220.127.116.11.3 If 1300 Hz is detected the modem shall connect as V.23. 5.2.9 If timer Tb expires, the modem shall remain silent for 75+/- 5 ms then transmit, for the duration of variable timer Tc (default 2 secs) depending on the user setting 1300 Hz carrier, 1650 Hz or 2125 Hz . The modem shall monitor for the appropriate response while transmitting one of the above carriers. 5.2.10 If Tc expires the modem shall proceed to the next appropriate probe (e.g. next carrier mode, or next carrierless mode). 5.3 Character conversion in 5-bit mode The initial condition of the converter shall be the Letters (LTRS) mode, therefore the modem shall send the LTRS character (11111) to the line prior to transmitting the first translated character. The receiver decoding shall also start up in the LTRS mode. Additionally, the modem shall send the appropriate mode character (i.e., LTRS or FIGS) every 72 characters. 5.3.1 The 5-bit codes supported are given in Tables B-1 and Tables B-2. Each character shall consist of the 5-bit sequence given in the tables preceded by a one start bit and followed by a minimum of one and one half stop bits. 5.3.2 The modem shall convert the 5-bit coded characters received from the line to the appropriate 7-bit coded characters and transfer them to the DTE on circuit 104 (or its equivalent) . 5.3.3 The modem shall convert the 7-bit coded characters received from the DTE on Circuit 103 (or its equivalent) to the appropriate 5-bit coded characters (see Annex A) and transmit to the line. 5.4 Character conversion in DTMF mode 5.4.1 The Recommendation Q.23 (DTMF) characters supported are given in Tables C-1 and C-2. Each character shall consist of the appropriate code sequence given in the table. 5.4.2 The modem shall convert the DTMF characters received from the line to their equivalent T.50 coded characters and transfer them to the DTE on circuit 104 (or its equivalent) per Table C-1. 5.4.3 The modem shall convert the Recommendation T.50 coded characters received from the DTE on Circuit 103 (or its equivalent) to the appropriate DTMF characters and transmit to the line per Table C-2. 5.5 Character conversion in the EDT mode Although no character conversion is required the EDT must use the following character structure. The 7-bit T.50 coded character shall be proceeded by one (1) START bit and shall be followed by one EVEN PARITY bit, and 2 STOP bits. Annex A 5 bit Operational Mode A.1 Mode of operation The communication channel is half-duplex with no channel turnaround. The receiver shall be disabled for 300 ms when a character is transmitted. A.2 Modulation The modulation is frequency shift keyed modulation (i.e. no carrier is present when a character is not being transmitted) using 1 400 Hz for a binary 1 and 1 800 Hz for a binary 0. A bit duration of either 20 or 22.00 0.40 ms is used providing either a nominal data signalling rate of 50 or 45.45 bits/s respectively. Annex B DTMF Operational Mode B.1 Mode of operation The communication channel is half-duplex. Annex C EDT Operational Mode C.1 Mode of operation The communications channel is half-duplex with no channel turnaround. The receiver is disabled for 300 ms when a character is transmitted. C.2 Modulation The modulation is frequency shift keyed modulation (i.e. carrier is 10 ms before a character is transmitted and removed 1s after the last character) using Recommendation V.21(1) frequencies. The data signalling rate is 110 bits/s. Annex D Bell 103 mode D.1 Mode of operation The communication circuit for data transmission is a duplex circuit whereby data transmission in both directions simultaneously is possible at 300 bit/s or less. The frequency of the ANS used by this modem is 2225 Hz. D.2 Modulation The modulation is a binary modulation obtained by frequency shift, resulting in a modulation rate being equal to the data signalling rate. For channel No. 1, the nominal mean frequency is 1170 Hz, For channel No. 2, it is 2125 Hz. The frequency deviation is ± 100 Hz. In each channel, the higher characteristic frequency (FA) corresponds to a binary 0. (i.e. channel No. 1 (FA = 1270 Hz and Fz = 1070 Hz); channel No. 2 (FA = 2225 Hz and Fz = 2025 Hz)). Appendix 1/V.18 Representative ordering of automoding The following orderings of automoding are suggested for the specified countries: USA CI detection period send 5 bit code buffered message, send ANS send Annex D carrier send V.21 carrier send V.23 carrier send EDT code buffered message send DTMF buffered message UK/Scandinavian Countries CI detection period send ANS send V.21 carrier send 5 bit code buffered message send V.23 carrier send EDT code buffered message send DTMF buffered message send Annex D carrier Australia, Ireland CI detection period send 5 bit code buffered message, send ANS send V.21 carrier send V.23 carrier send EDT code buffered message send DTMF buffered message send Annex D carrier Germany, Switzerland CI detection period send EDT code buffered message, send ANS send V.21 carrier send V.23 carrier send 5-bit code buffered message send DTMF buffered message send Annex D carrier Netherlands CI detection period send DTMF buffered message, send ANS send V.21 carrier send V.23 carrier send 5 bit code buffered message send EDT buffered message send Annex D carrier Annex 2 Guidelines For Text Telephones Used With Recommendation V.18 Character set and control The recommended initial character format when two V.18 modems are interconnected is 8 bits data and no parity bit. The initial character set provided should be in accordance with ISO 8859-1. There should also be provision made for changing the character set using the control procedures specified in ISO 6429. The following minimal set of presentation control functions should be supported: carriage return, line feed, back space, select character. The erasure of characters should be controlled by the sending party only. Visual presentation It is recommended that sent and received characters be presented in separate areas of the display or at a minimum be assigned distinctive fonts to allow for easy determination of the conversation flow by the users. Line status display Visual indications on the status of the connection should be visually presented, including call progress information as well as the status of Circuit 135, line energy present.