diff --git a/fskmodem.c b/fskmodem.c
new file mode 100755
index 0000000000000000000000000000000000000000..554bb941090257ec4f2376791eff7f4f38863a13
--- /dev/null
+++ b/fskmodem.c
@@ -0,0 +1,283 @@
+/*
+ * Asterisk -- A telephony toolkit for Linux.
+ *
+ * FSK Modulator/Demodulator
+ *
+ * Copyright (C) 1999, Mark Spencer
+ *
+ * Mark Spencer <markster@linux-support.net>
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License.
+ *
+ * Includes code and algorithms from the Zapata library.
+ *
+ */
+
+#include <asterisk/fskmodem.h>
+
+#include <stdio.h>
+
+#define NBW 2
+#define BWLIST {75,800}
+#define NF 4
+#define FLIST {1400,1800,1200,2200}
+
+#define STATE_SEARCH_STARTBIT 0
+#define STATE_SEARCH_STARTBIT2 1
+#define STATE_SEARCH_STARTBIT3 2
+#define STATE_GET_BYTE 3
+
+static inline float get_sample(short **buffer, int *len)
+{
+ float retval;
+ retval = (float) **buffer / 256;
+ (*buffer)++;
+ (*len)--;
+ return retval;
+}
+
+#define GET_SAMPLE get_sample(&buffer, len)
+
+/* Coeficientes para filtros de entrada */
+/* Tabla de coeficientes, generada a partir del programa "mkfilter" */
+/* Formato: coef[IDX_FREC][IDX_BW][IDX_COEF] */
+/* IDX_COEF=0 => 1/GAIN */
+/* IDX_COEF=1-6 => Coeficientes y[n] */
+
+static double coef_in[NF][NBW][8]={
+#include "coef_in.h"
+};
+
+/* Coeficientes para filtro de salida */
+/* Tabla de coeficientes, generada a partir del programa "mkfilter" */
+/* Formato: coef[IDX_BW][IDX_COEF] */
+/* IDX_COEF=0 => 1/GAIN */
+/* IDX_COEF=1-6 => Coeficientes y[n] */
+
+static double coef_out[NBW][8]={
+#include "coef_out.h"
+};
+
+
+/* Filtro pasa-banda para frecuencia de MARCA */
+static inline float filtroM(fsk_data *fskd,float in)
+{
+ int i,j;
+ double s;
+ double *pc;
+
+ pc=&coef_in[fskd->f_mark_idx][fskd->bw][0];
+ fskd->fmxv[(fskd->fmp+6)&7]=in*(*pc++);
+
+ s=(fskd->fmxv[(fskd->fmp+6)&7] - fskd->fmxv[fskd->fmp]) + 3 * (fskd->fmxv[(fskd->fmp+2)&7] - fskd->fmxv[(fskd->fmp+4)&7]);
+ for (i=0,j=fskd->fmp;i<6;i++,j++) s+=fskd->fmyv[j&7]*(*pc++);
+ fskd->fmyv[j&7]=s;
+ fskd->fmp++; fskd->fmp&=7;
+ return s;
+}
+
+/* Filtro pasa-banda para frecuencia de ESPACIO */
+static inline float filtroS(fsk_data *fskd,float in)
+{
+ int i,j;
+ double s;
+ double *pc;
+
+ pc=&coef_in[fskd->f_space_idx][fskd->bw][0];
+ fskd->fsxv[(fskd->fsp+6)&7]=in*(*pc++);
+
+ s=(fskd->fsxv[(fskd->fsp+6)&7] - fskd->fsxv[fskd->fsp]) + 3 * (fskd->fsxv[(fskd->fsp+2)&7] - fskd->fsxv[(fskd->fsp+4)&7]);
+ for (i=0,j=fskd->fsp;i<6;i++,j++) s+=fskd->fsyv[j&7]*(*pc++);
+ fskd->fsyv[j&7]=s;
+ fskd->fsp++; fskd->fsp&=7;
+ return s;
+}
+
+/* Filtro pasa-bajos para datos demodulados */
+static inline float filtroL(fsk_data *fskd,float in)
+{
+ int i,j;
+ double s;
+ double *pc;
+
+ pc=&coef_out[fskd->bw][0];
+ fskd->flxv[(fskd->flp + 6) & 7]=in * (*pc++);
+
+ s= (fskd->flxv[fskd->flp] + fskd->flxv[(fskd->flp+6)&7]) +
+ 6 * (fskd->flxv[(fskd->flp+1)&7] + fskd->flxv[(fskd->flp+5)&7]) +
+ 15 * (fskd->flxv[(fskd->flp+2)&7] + fskd->flxv[(fskd->flp+4)&7]) +
+ 20 * fskd->flxv[(fskd->flp+3)&7];
+
+ for (i=0,j=fskd->flp;i<6;i++,j++) s+=fskd->flyv[j&7]*(*pc++);
+ fskd->flyv[j&7]=s;
+ fskd->flp++; fskd->flp&=7;
+ return s;
+}
+
+static inline int demodulador(fsk_data *fskd, float *retval, float x)
+{
+ float xS,xM;
+
+ fskd->cola_in[fskd->pcola]=x;
+
+ xS=filtroS(fskd,x);
+ xM=filtroM(fskd,x);
+
+ fskd->cola_filtro[fskd->pcola]=xM-xS;
+
+ x=filtroL(fskd,xM*xM - xS*xS);
+
+ fskd->cola_demod[fskd->pcola++]=x;
+ fskd->pcola &= (NCOLA-1);
+
+ *retval = x;
+ return(0);
+}
+
+static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
+{
+ /* Esta funcion implementa un DPLL para sincronizarse con los bits */
+ float x,spb,spb2,ds;
+ int f;
+
+ spb=fskd->spb;
+ if (fskd->spb == 7) spb = 8000.0 / 1200.0;
+ ds=spb/32.;
+ spb2=spb/2.;
+
+ for (f=0;;){
+ if (demodulador(fskd,&x, GET_SAMPLE)) return(-1);
+ if ((x*fskd->x0)<0) { /* Transicion */
+ if (!f) {
+ if (fskd->cont<(spb2)) fskd->cont+=ds; else fskd->cont-=ds;
+ f=1;
+ }
+ }
+ fskd->x0=x;
+ fskd->cont+=1.;
+ if (fskd->cont>spb) {
+ fskd->cont-=spb;
+ break;
+ }
+ }
+ f=(x>0)?0x80:0;
+ return(f);
+}
+
+int fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte)
+{
+ int a;
+ int i,j,n1,r;
+ int samples=0;
+ int olen;
+ switch(fskd->state) {
+ /* Pick up where we left off */
+ case STATE_SEARCH_STARTBIT2:
+ goto search_startbit2;
+ case STATE_SEARCH_STARTBIT3:
+ goto search_startbit3;
+ case STATE_GET_BYTE:
+ goto getbyte;
+ }
+ /* Esperamos bit de start */
+ do {
+/* this was jesus's nice, reasonable, working (at least with RTTY) code
+to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
+just start sending a start bit with nothing preceding it at the beginning
+of a transmission (what a LOSING design), we cant do it this elegantly */
+/*
+ if (demodulador(zap,&x1)) return(-1);
+ for(;;) {
+ if (demodulador(zap,&x2)) return(-1);
+ if (x1>0 && x2<0) break;
+ x1=x2;
+ }
+*/
+/* this is now the imprecise, losing, but functional code to detect the
+beginning of a start bit in the TDD sceanario. It just looks for sufficient
+level to maybe, perhaps, guess, maybe that its maybe the beginning of
+a start bit, perhaps. This whole thing stinks! */
+ if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
+ samples++;
+ for(;;)
+ {
+search_startbit2:
+ if (!*len) {
+ fskd->state = STATE_SEARCH_STARTBIT2;
+ return 0;
+ }
+ samples++;
+ if (demodulador(fskd,&fskd->x2,GET_SAMPLE)) return(-1);
+#if 0
+ printf("x2 = %5.5f ", fskd->x2);
+#endif
+ if (fskd->x2 < -0.5) break;
+ }
+search_startbit3:
+ /* Esperamos 0.5 bits antes de usar DPLL */
+ i=fskd->spb/2;
+ if (*len < i) {
+ fskd->state = STATE_SEARCH_STARTBIT3;
+ return 0;
+ }
+ for(;i;i--) { if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
+#if 0
+ printf("x1 = %5.5f ", fskd->x1);
+#endif
+ samples++; }
+
+ /* x1 debe ser negativo (confirmación del bit de start) */
+
+ } while (fskd->x1>0);
+ fskd->state = STATE_GET_BYTE;
+
+getbyte:
+
+ /* Need at least 80 samples to be sure we'll have a byte */
+ if (*len < 80)
+ return 0;
+
+ /* Leemos ahora los bits de datos */
+ j=fskd->nbit;
+ for (a=n1=0;j;j--) {
+ olen = *len;
+ i=get_bit_raw(fskd, buffer, len);
+ buffer += (olen - *len);
+ if (i == -1) return(-1);
+ if (i) n1++;
+ a>>=1; a|=i;
+ }
+ j=8-fskd->nbit;
+ a>>=j;
+
+ /* Leemos bit de paridad (si existe) y la comprobamos */
+ if (fskd->paridad) {
+ olen = *len;
+ i=get_bit_raw(fskd, buffer, len);
+ buffer += (olen - *len);
+ if (i == -1) return(-1);
+ if (i) n1++;
+ if (fskd->paridad==1) { /* paridad=1 (par) */
+ if (n1&1) a|=0x100; /* error */
+ } else { /* paridad=2 (impar) */
+ if (!(n1&1)) a|=0x100; /* error */
+ }
+ }
+
+ /* Leemos bits de STOP. Todos deben ser 1 */
+
+ for (j=fskd->nstop;j;j--) {
+ r = get_bit_raw(fskd, buffer, len);
+ if (r == -1) return(-1);
+ if (!r) a|=0x200;
+ }
+
+ /* Por fin retornamos */
+ /* Bit 8 : Error de paridad */
+ /* Bit 9 : Error de Framming */
+
+ *outbyte = a;
+ fskd->state = STATE_SEARCH_STARTBIT;
+ return 1;
+}
diff --git a/include/asterisk/fskmodem.h b/include/asterisk/fskmodem.h
new file mode 100755
index 0000000000000000000000000000000000000000..61a77449fd242ed2fbf79038cbabc7ad2c1287f1
--- /dev/null
+++ b/include/asterisk/fskmodem.h
@@ -0,0 +1,63 @@
+/*
+ * Asterisk -- A telephony toolkit for Linux.
+ *
+ * FSK Modem Support
+ *
+ * Copyright (C) 1999, Mark Spencer
+ *
+ * Mark Spencer <markster@linux-support.net>
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License.
+ *
+ * Includes code and algorithms from the Zapata library.
+ *
+ */
+
+#ifndef _FSKMODEM_H
+#define _FSKMODEM_H
+
+#define PARITY_NONE 0
+#define PARITY_EVEN 1
+#define PARITY_ODD 2
+
+
+#define NCOLA 0x4000
+
+typedef struct {
+ float spb; /* Samples / Bit */
+ int nbit; /* Number of Data Bits (5,7,8) */
+ float nstop; /* Number of Stop Bits 1,1.5,2 */
+ int paridad; /* Parity 0=none 1=even 2=odd */
+ int hdlc; /* Modo Packet */
+ float x0;
+ float x1;
+ float x2;
+ float cont;
+ int bw; /* Ancho de Banda */
+ double fmxv[8],fmyv[8]; /* filter stuff for M filter */
+ int fmp; /* pointer for M filter */
+ double fsxv[8],fsyv[8]; /* filter stuff for S filter */
+ int fsp; /* pointer for S filter */
+ double flxv[8],flyv[8]; /* filter stuff for L filter */
+ int flp; /* pointer for L filter */
+ int f_mark_idx; /* Indice de frecuencia de marca (f_M-500)/5 */
+ int f_space_idx;/* Indice de frecuencia de espacio (f_S-500)/5 */
+ int state;
+ int pcola; /* Puntero de las colas de datos */
+ float cola_in[NCOLA]; /* Cola de muestras de entrada */
+ float cola_filtro[NCOLA]; /* Cola de muestras tras filtros */
+ float cola_demod[NCOLA]; /* Cola de muestras demoduladas */
+} fsk_data;
+
+/* Retrieve a serial byte into outbyte. Buffer is a pointer into a series of
+ shorts and len records the number of bytes in the buffer. len will be
+ overwritten with the number of bytes left that were not consumed, and the
+ return value is as follows:
+ 0: Still looking for something...
+ 1: An output byte was received and stored in outbyte
+ -1: An error occured in the transmission
+ He must be called with at least 80 bytes of buffer. */
+extern int fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte);
+
+#endif