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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * fax.h - definitions for analogue line ITU T.30 fax processing
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2005 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: fax.h,v 1.20 2006/10/24 13:45:28 steveu Exp $
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26 */
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27
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28 /*! \file */
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29
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30 #if !defined(_FAX_H_)
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31 #define _FAX_H_
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32
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33 /*! \page fax_page FAX over analogue modem handling
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34
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35 \section fax_page_sec_1 What does it do?
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36
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37 \section fax_page_sec_2 How does it work?
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38 */
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39
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40 typedef struct fax_state_s fax_state_t;
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41
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42 typedef void (fax_flush_handler_t)(fax_state_t *s, void *user_data, int which);
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43
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44 /*!
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45 Analogue line T.30 FAX channel descriptor. This defines the state of a single working
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46 instance of an analogue line soft-FAX machine.
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47 */
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48 struct fax_state_s
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49 {
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50 /* This must be kept the first thing in the structure, so it can be pointed
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51 to reliably as the structures change over time. */
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52 t30_state_t t30_state;
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53
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54 /*! TRUE is talker echo protection should be sent for the image modems */
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55 int use_tep;
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56
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57 fax_flush_handler_t *flush_handler;
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58 void *flush_user_data;
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59
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60 /*! The current receive signal handler */
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61 span_rx_handler_t *rx_handler;
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62 void *rx_user_data;
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63
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64 /*! The current transmit signal handler */
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65 span_tx_handler_t *tx_handler;
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66 void *tx_user_data;
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67 int tx_hdlc_preamble_len;
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68 /*! The transmit signal handler to be used when the current one has finished sending. */
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69 span_tx_handler_t *next_tx_handler;
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70 void *next_tx_user_data;
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71
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72 /*! If TRUE, transmission is in progress */
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73 int transmit;
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74
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75 /*! If TRUE, transmit silence when there is nothing else to transmit. If FALSE return only
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76 the actual generated audio. Note that this only affects untimed silences. Timed silences
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77 (e.g. the 75ms silence between V.21 and a high speed modem) will alway be transmitted as
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78 silent audio. */
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79 int transmit_on_idle;
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80
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81 /*! \brief A tone generator context used to generate supervisory tones during
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82 FAX handling. */
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83 tone_gen_state_t tone_gen;
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84 /*! \brief An HDLC context used when receiving HDLC over V.21 messages. */
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85 hdlc_rx_state_t hdlcrx;
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86 /*! \brief An HDLC context used when transmitting HDLC over V.21 messages. */
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87 hdlc_tx_state_t hdlctx;
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88 /*! \brief A V.21 FSK modem context used when transmitting HDLC over V.21
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89 messages. */
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90 fsk_tx_state_t v21tx;
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91 /*! \brief A V.21 FSK modem context used when receiving HDLC over V.21
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92 messages. */
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93 fsk_rx_state_t v21rx;
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94 #if defined(ENABLE_V17)
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95 /*! \brief A V.17 modem context used when sending FAXes at 7200bps, 9600bps
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96 12000bps or 14400bps*/
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97 v17_tx_state_t v17tx;
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98 /*! \brief A V.29 modem context used when receiving FAXes at 7200bps, 9600bps
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99 12000bps or 14400bps*/
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100 v17_rx_state_t v17rx;
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101 #endif
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102 /*! \brief A V.27ter modem context used when sending FAXes at 2400bps or
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103 4800bps */
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104 v27ter_tx_state_t v27ter_tx;
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105 /*! \brief A V.27ter modem context used when receiving FAXes at 2400bps or
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106 4800bps */
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107 v27ter_rx_state_t v27ter_rx;
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108 /*! \brief A V.29 modem context used when sending FAXes at 7200bps or
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109 9600bps */
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110 v29_tx_state_t v29tx;
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111 /*! \brief A V.29 modem context used when receiving FAXes at 7200bps or
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112 9600bps */
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113 v29_rx_state_t v29rx;
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114 /*! \brief Used to insert timed silences. */
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115 silence_gen_state_t silence_gen;
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116 /*! \brief */
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117 dc_restore_state_t dc_restore;
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118
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119 /*! \brief TRUE is the short training sequence should be used. */
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120 int short_train;
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121
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122 /*! The currently select receiver type */
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123 int current_rx_type;
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124 /*! The currently select transmitter type */
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125 int current_tx_type;
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126
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127 int first_tx_hdlc_frame;
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128
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129 /*! Audio logging file handles */
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130 int fax_audio_rx_log;
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131 int fax_audio_tx_log;
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132 /*! \brief Error and flow logging control */
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133 logging_state_t logging;
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134 };
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135
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136 #ifdef __cplusplus
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137 extern "C" {
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138 #endif
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139
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140 /*! Apply T.30 receive processing to a block of audio samples.
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141 \brief Apply T.30 receive processing to a block of audio samples.
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142 \param s The FAX context.
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143 \param amp The audio sample buffer.
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144 \param len The number of samples in the buffer.
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145 \return The number of samples unprocessed. This should only be non-zero if
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146 the software has reached the end of the FAX call.
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147 */
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148 int fax_rx(fax_state_t *s, int16_t *amp, int len);
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149
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150 /*! Apply T.30 transmit processing to generate a block of audio samples.
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151 \brief Apply T.30 transmit processing to generate a block of audio samples.
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152 \param s The FAX context.
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153 \param amp The audio sample buffer.
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154 \param max_len The number of samples to be generated.
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155 \return The number of samples actually generated. This will be zero when
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156 there is nothing to send.
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157 */
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158 int fax_tx(fax_state_t *s, int16_t *amp, int max_len);
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159
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160 void fax_set_flush_handler(fax_state_t *s, fax_flush_handler_t *handler, void *user_data);
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161
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162 /*! Select whether silent audio will be sent when FAX transmit is idle.
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163 \brief Select whether silent audio will be sent when FAX transmit is idle.
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164 \param s The FAX context.
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165 \param transmit_on_idle TRUE if silent audio should be output when the FAX transmitter is
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166 idle. FALSE to transmit zero length audio when the FAX transmitter is idle. The default
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167 behaviour is FALSE.
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168 */
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169 void fax_set_transmit_on_idle(fax_state_t *s, int transmit_on_idle);
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170
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171 /*! Select whether talker echo protection tone will be sent for the image modems.
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172 \brief Select whether TEP will be sent for the image modems.
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173 \param s The FAX context.
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174 \param use_tep TRUE if TEP should be sent.
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175 */
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176 void fax_set_tep_mode(fax_state_t *s, int use_tep);
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177
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178 /*! Initialise a FAX context.
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179 \brief Initialise a FAX context.
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180 \param s The FAX context.
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181 \param calling_party TRUE if the context is for a calling party. FALSE if the
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182 context is for an answering party.
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183 \return 0 for OK, else -1.
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184 */
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185 int fax_init(fax_state_t *s, int calling_party);
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186
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187 /*! Release a FAX context.
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188 \brief Release a FAX context.
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189 \param s The FAX context. */
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190 int fax_release(fax_state_t *s);
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191
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192 #ifdef __cplusplus
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193 }
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194 #endif
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195
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196 #endif
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197 /*- End of file ------------------------------------------------------------*/
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