2 * \file beacon.hxx -- Provides marker beacon audio generation.
5 // Written by Curtis Olson, started March 2001.
7 // Copyright (C) 2001 Curtis L. Olson - http://www.flightgear.org/~curt
9 // This program is free software; you can redistribute it and/or
10 // modify it under the terms of the GNU General Public License as
11 // published by the Free Software Foundation; either version 2 of the
12 // License, or (at your option) any later version.
14 // This program is distributed in the hope that it will be useful, but
15 // WITHOUT ANY WARRANTY; without even the implied warranty of
16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 // General Public License for more details.
19 // You should have received a copy of the GNU General Public License
20 // along with this program; if not, write to the Free Software
21 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
33 #include <simgear/compiler.h>
34 #include <simgear/sound/soundmgr_openal.hxx>
35 #include <simgear/structure/SGReferenced.hxx>
36 #include <simgear/structure/SGSharedPtr.hxx>
41 // Quoting from http://www.smartregs.com/data/sa326.htm
42 // Smart REGS Glossary - marker beacon
44 // An electronic navigation facility transmitting a 75 MHz vertical fan
45 // or boneshaped radiation pattern. Marker beacons are identified by
46 // their modulation frequency and keying code, and when received by
47 // compatible airborne equipment, indicate to the pilot, both aurally
48 // and visually, that he is passing over the facility.
49 // (See outer marker middle marker inner marker.)
51 // Smart REGS Glossary - outer marker
53 // A marker beacon at or near the glideslope intercept altitude of an
54 // ILS approach. It is keyed to transmit two dashes per second on a
55 // 400 Hz tone, which is received aurally and visually by compatible
56 // airborne equipment. The OM is normally located four to seven miles from
57 // the runway threshold on the extended centerline of the runway.
59 // Smart REGS Glossary - middle marker
61 // A marker beacon that defines a point along the glideslope of an
62 // ILS normally located at or near the point of decision height
63 // (ILS Category I). It is keyed to transmit alternate dots and dashes,
64 // with the alternate dots and dashes keyed at the rate of 95 dot/dash
65 // combinations per minute on a 1300 Hz tone, which is received
66 // aurally and visually by compatible airborne equipment.
68 // Smart REGS Glossary - inner marker
70 // A marker beacon used with an ILS (CAT II) precision approach located
71 // between the middle marker and the end of the ILS runway,
72 // transmitting a radiation pattern keyed at six dots per second and
73 // indicating to the pilot, both aurally and visually, that he is at
74 // the designated decision height (DH), normally 100 feet above the
75 // touchdown zone elevation, on the ILS CAT II approach. It also marks
76 // progress during a CAT III approach.
77 // (See instrument landing system) (Refer to AIM.)
80 static const int INNER_FREQ = 3000;
81 static const int MIDDLE_FREQ = 1300;
82 static const int OUTER_FREQ = 400;
84 static const int INNER_SIZE = BYTES_PER_SECOND;
85 static const int MIDDLE_SIZE = (int)(BYTES_PER_SECOND * 60 / 95 );
86 static const int OUTER_SIZE = BYTES_PER_SECOND;
88 static const int INNER_DIT_LEN = (int)(BYTES_PER_SECOND / 6.0);
89 static const int MIDDLE_DIT_LEN = (int)(MIDDLE_SIZE / 3.0);
90 static const int MIDDLE_DAH_LEN = (int)(MIDDLE_SIZE * 2 / 3.0);
91 static const int OUTER_DAH_LEN = (int)(BYTES_PER_SECOND / 2.0);
93 // manages everything we need to know for an individual sound sample
98 SGSharedPtr<SGSoundSample> inner;
99 SGSharedPtr<SGSoundSample> middle;
100 SGSharedPtr<SGSoundSample> outer;
107 // allocate and initialize sound samples
110 SGSoundSample *get_inner() { return inner; }
111 SGSoundSample *get_middle() { return middle; }
112 SGSoundSample *get_outer() { return outer; }
118 #endif // _BEACON_HXX