Work on docs
Andreas Eversberg
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<html>
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<head>
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<link href="style.css" rel="stylesheet" type="text/css" />
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<title>osmocom-analog</title>
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</head>
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<body>
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<center><table><tr><td>
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<h2><center>Das Datenklo</center></h2>
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<center><img src="datenklo.jpg"/></center>
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<ul>
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<li><a href="#history">History</a>
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<li><a href="#howitworks">How it works</a>
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<li><a href="#terminal">Setup of a terminal</a>
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</ul>
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<p class="toppic">
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<a name="history"></a>
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History
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</p>
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<p>
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geschichte
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name
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was kann der chip
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TBD
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</p>
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<center><img src="datenklo2.jpg"/></center>
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<p class="toppic">
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<a name="howitworks"></a>
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How it works
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</p>
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<p>
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The program 'datenklo' is an emulator for the original "CCC modem", a building instruction released by the Chaos Computer Club in 1985.
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The heart of this software is the AM7911 modem chip emulation.
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It modulates digital levels to FSK tones and demodulates FSK tones to digital levels.
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A software UART (serial transceiver) converts characters (bytes) into levels and leves into bytes.
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The modem chip emulation is linked to sound card via ALSA driver.
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The UART is linked to a tty emulation.
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The tty emulation uses FUSE, so that the linux kernel provides a virtual serial interface. (/dev/ttyDATENKLO0 by default)
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</p>
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<p>
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* TBD *
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</p>
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<p class="toppic">
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<a name="terminal"></a>
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Setup of a terminal
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</p>
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<p>
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* TBD *
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</p>
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<hr><center>[<a href="index.html">Back to main page</a>]</center><hr>
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</td></tr></table></center>
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</body>
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</html>
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<html>
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<head>
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<link href="style.css" rel="stylesheet" type="text/css" />
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<title>osmocom-analog</title>
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</head>
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<body>
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<center><table><tr><td>
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<h2><center>Eurosignal</center></h2>
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<center><img src="eurosignal.jpg"/></center>
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<ul>
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<li><a href="#history">History</a>
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<li><a href="#howitworks">How it works</a>
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<li><a href="#basestation">Setup of a base station</a>
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</ul>
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<p class="toppic">
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<a name="history"></a>
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History
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</p>
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<p>
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Eurosignal (a.k.a Europäischer Funkrufdienst EFuRD) was a paging service in Europe.
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It was introduced in 1974 in Germany, 1975 in France and 1985 in Switzerland.
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The system was shut down in France and Switzerland in 31. December 1997, in Germany on 1. April 1998.
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It did not support any message forwarding.
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An incoming call was indicated as a beep (and/or vibration) by the pager.
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But up to 4 paging IDs could be assigned to one single device.
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The device showed which ID was paged.
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</p>
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<p>
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Paging a subscriber was done via telephone dial up.
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The prefix was assigned to large areas having multiple transmitters with the same frequency/channel.
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(In Germany were three areas: North, Middle, South)
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The suffix (the pager ID) was then encoded into tones and transmitted with up to 2 KW of power.
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The pager device decoded the tones and checked if they match with the assigned ID.
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Inside the pager were jumpers and later a chip with diodes to match the received tone sequence with the assigned ID.
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Up to four numbers were assigned to one pager.
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</p>
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<p>
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One may remember the sound at the beginning of the FM broadcast band:
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</p>
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<center>Listen to the base station's paging sequences:<br>
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<audio src="eurosignal.wav" controls></audio></center>
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<p>
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Check out <a href="http://www.oebl.de">oebl.de</a> for much more detailed description in German.
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</p>
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<p class="toppic">
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<a name="howitworks"></a>
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How it works
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</p>
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<p>
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4 frequencies were used by the system:
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</p>
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<ul>
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<li>Channel A: 87,340 MHz
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<li>Channel B: 87,365 MHz
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<li>Channel C: 87,390 MHz
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<li>Channel D: 87,415 MHz
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</ul>
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<p>
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The caller calls a prefix followed by a 6 digits number.
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The system puts the number into a queue, so that simultaneous calls can be handled and paging is performed in series.
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</p>
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<p>
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A train of paging messages are transmitted without interruption.
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There are two types of messages: A paging message and an idle message.
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Each message was about 8.2 seconds long, divided into a sequence of tones.
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</p>
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<p>
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This is how a paging message looks like:
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</p>
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<pre class="list">
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+---------------+-------+-------+-------+-------+-------+-------+
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| Idle | Digit | Digit | Digit | Digit | Digit | Digit |
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| Tone | 1 | 2 | 3 | 4 | 5 | 6 |
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+---------------+-------+-------+-------+-------+-------+-------+
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220 ms 100 ms 100 ms 100 ms 100 ms 100 ms 100 ms
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</pre>
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<p>
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The digit clock is retrieved from the change of tones.
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If two subsequent digits are the same, the second digit was replaced by a 'Repeat' digit, so that there is always a change of tone between digits.
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The Idle tone resets the receiver register and indicates a new message.
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A pager ID '122233' would be transmitted as 1-2-R-2-3-R.
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A message is repeated multiple times, depending on the load of the system. (2-5 times ???)
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If there is no message to be transmitted, the following idle message is sent.
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</p>
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<p>
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This is how an idle message looks like:
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</p>
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<pre class="list">
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+---------------+-------+---------------------------------------+
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| Idle | Digit | Idle |
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| Tone | R | Tone |
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+---------------+-------+---------------------------------------+
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220 ms 100 ms 500 ms
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</pre>
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<p>
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Here is a list of all frequencies used.
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The distance between frequencies increases on higher frequencies, allowing simple RC filters to be used to detect the tones.
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</p>
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<pre class="list">
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Digit / Tone | Frequency
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--------------+----------------
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Idle | 1153.1 Hz
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Repeat | 1062.9 Hz
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0 | 979.8 Hz
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1 | 903.1 Hz
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2 | 832.5 Hz
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3 | 767.4 Hz
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4 | 707.4 Hz
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5 | 652.0 Hz
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6 | 601.0 Hz
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7 | 554.0 Hz
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8 | 510.7 Hz
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9 | 470.8 Hz
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Spare 1 | 433.9 Hz
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Spare 2 | 400.0 Hz
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Spare 3 | 368.7 Hz
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Spare 4 | 339.9 Hz
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Spare 5 | 313.3 Hz
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</pre>
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<p>
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The message is amplitude modulated.
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The modulation index is 92 %.
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</p>
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<p>
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Alternatively the signal can be transmitted frequency modulated, to reduce interference with TV stations.
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The frequency is shifted by 7.5 KHz above or below the actual channel frequency.
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The frequency deviation causes a change of amplitude in the demodulator of the pager, so it works as well.
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</p>
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<p class="toppic">
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<a name="basestation"></a>
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Setup of a base station
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</p>
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<p>
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Find out what channel your pager can receive and select the same channel on the transmitting side.
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Assume that your pager is set to channel B, select channel B:
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</p>
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<pre>
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# src/eurosignal/eurosignal -k B
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...
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eurosignal.c:290 notice : Created 'Kanal' B
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Base station for channel B ready, please tune transmitter and/or receiver to 87.3650 MHz
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...
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</pre>
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<p>
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If you don't have a FM transmitter instead of an AM transmitter, tune it 7.5 KHz below or above the indicated channel.
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I suggest to use SDR, so check out the SDR page.
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Then enter the ID of your pager. You will find it printed on the device and/or on the 18 pin chip inside.
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If your pager's ID is 123456, enter it and press 'd' to start paging:
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</p>
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<pre>
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on-hook: 123456 (press d=dial)
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mncc_console.c:358 info : Outgoing call to '123456'
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call.c:699 info : Received MNCC call from fixed network '' to mobile '123456'
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call.c:706 info : Indicate MNCC call confirm towards fixed network
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call.c:717 info : Outgoing call from '' to '123456'
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eurosignal.c:318 info : Creating call instance to page ID '123456'.
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call.c:478 info : Call has been answered by '123456'
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call.c:466 info : Indicate MNCC answer towards fixed network
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mncc_console.c:206 info : Call connected to '123456'
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eurosignal.c:605 info : Station acknowledges, playing announcement.
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eurosignal.c:387 notice : Transmitting ID '123456'.
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eurosignal.c:387 notice : Transmitting ID '123456'.
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eurosignal.c:387 notice : Transmitting ID '123456'.
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eurosignal.c:387 notice : Transmitting ID '123456'.
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mncc_console.c:388 info : Call hangup
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call.c:774 info : Received MNCC release from fixed network with cause 16
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call.c:778 info : Call released toward mobile network
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eurosignal.c:760 info : Call has been disconnected by network.
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</pre>
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<p>
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In order to receive a paging message, use -R (--rx).
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Then the software will decode the received IDs and display them.
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</p>
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<hr><center>[<a href="index.html">Back to main page</a>]</center><hr>
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</td></tr></table></center>
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</body>
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</html>
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@ -38,6 +38,14 @@
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<th>MTS / IMTS (USA / Canada)</th>
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<th>AMPS (USA) / TACS (UK / Ireland / Italy)</th>
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</tr>
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<tr>
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<td><img src="eurosignal_small.jpg" title="Eurosignal paging service"/></td>
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<td><img src="datenklo_small.jpg" title="The Chaos Computer Club Modem"/></td>
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</tr>
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<tr>
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<th>Eurosignal paging service</th>
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<th>The Chaos Computer Club Modem</th>
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</tr>
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<tr>
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<td><img src="tv_small.jpg" title="TV signal generator and transmitter"/></td>
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<td><img src="setup_small.jpg"/></td>
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@ -92,6 +100,7 @@ Implemented networks:
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<li><a href="amps.html">AMPS - Advanced Mobile Phone Service</a> (USA)</li>
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<li><a href="tacs.html">TACS / JTACS - Total Access Communication System</a> (UK/Italy/Japan)</li>
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<li><a href="radiocom2000.html">Radiocom 2000</a> (France)</li>
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<li><a href="eurosignal.html">Eurosignal</a> (Europe)</li>
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</ul>
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</center>
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@ -101,6 +110,7 @@ Additional features:
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<center>
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<ul>
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<li><a href="datenklo.html">Das Datenklo</a></li>
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<li><a href="tv.html">Osmo TV</a></li>
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</ul>
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</center>
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