osmocom-analog

## Eurosignal History How it works Setup of a base station Make your own station ID ROM History Eurosignal (a.k.a Europäischer Funkrufdienst EFuRD) was a paging service in Europe. It was introduced in 1974 in Germany, 1975 in France and 1985 in Switzerland. The system was shut down in France and Switzerland in 31. December 1997, in Germany on 1. April 1998. It did not support any message forwarding. An incoming call was indicated as a beep (and/or vibration) by the pager. But up to 4 paging IDs could be assigned to one single device. The device showed which ID was paged. Paging a subscriber was done via telephone dial up. The prefix was assigned to large areas having multiple transmitters with the same frequency/channel. (In Germany were three areas: North, Middle, South) The suffix (the pager ID) was then encoded into tones and transmitted with up to 2 KW of power. The pager device decoded the tones and checked if they match with the assigned ID. Inside the pager were jumpers and later a chip with diodes to match the received tone sequence with the assigned ID. Up to four numbers were assigned to one pager. One may remember the sound at the beginning of the FM broadcast band: Listen to the base station's paging sequences: Check out oebl.de for much more detailed description in German. How it works 4 frequencies were used by the system: Channel A: 87,340 MHz Channel B: 87,365 MHz Channel C: 87,390 MHz Channel D: 87,415 MHz The caller calls a prefix followed by a 6 digits number. The system puts the number into a queue, so that simultaneous calls can be handled and paging is performed in series. A train of paging messages are transmitted without interruption. There are two types of messages: A paging message and an idle message. Each message is 0.82 seconds long, divided into a sequence of tones. This is how a paging message looks like:
    +---------------+-------+-------+-------+-------+-------+-------+
    |     Idle      | Digit | Digit | Digit | Digit | Digit | Digit |
    |     Tone      |   1   |   2   |   3   |   4   |   5   |   6   |
    +---------------+-------+-------+-------+-------+-------+-------+
          220 ms      100 ms  100 ms  100 ms  100 ms  100 ms  100 ms
The digit clock is retrieved from the change of tones. 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. The Idle tone indicates a new message and resets the receiver's register to start over receiving a message. A pager ID '122233' would be transmitted as 1-2-R-2-3-R. A message is repeated multiple times, depending on the load of the system. (2-5 times ???) If there is no message to be transmitted, the following idle message is sent. This is how an idle message looks like:
    +---------------+-------+---------------------------------------+
    |     Idle      | Digit |                 Idle                  |
    |     Tone      |   R   |                 Tone                  |
    +---------------+-------+---------------------------------------+
          220 ms      100 ms                  500 ms
Here is a list of all frequencies used. The distances between frequencies increase on higher frequencies (proportional to the frequency), allowing simple RC filters to be used to detect the tones.
     Digit / Tone | Frequency
    --------------+----------------
         Idle     | 1153.1 Hz
        Repeat    | 1062.9 Hz
          0       | 979.8 Hz
          1       | 903.1 Hz
          2       | 832.5 Hz
          3       | 767.4 Hz
          4       | 707.4 Hz
          5       | 652.0 Hz
          6       | 601.0 Hz
          7       | 554.0 Hz
          8       | 510.7 Hz
          9       | 470.8 Hz
       Spare 1    | 433.9 Hz
       Spare 2    | 400.0 Hz
       Spare 3    | 368.7 Hz
       Spare 4    | 339.9 Hz
       Spare 5    | 313.3 Hz
The message is amplitude modulated. The modulation index is 92 %. Alternatively the signal can be transmitted frequency modulated, to reduce interference with TV stations. The frequency is shifted by 7.5 KHz above or below the actual channel frequency. The frequency deviation causes a change of amplitude in the demodulator of the pager, so it works as well. Setup of a base station Find out what channel your pager can receive and select the same channel on the transmitting side. Assume that your pager is set to channel B, select channel B:
    # src/eurosignal/eurosignal -k B

    ...
    eurosignal.c:290 notice : Created 'Kanal' B
    Base station for channel B ready, please tune transmitter and/or receiver to 87.3650 MHz
    ...
If you have an FM transmitter instead of an AM transmitter, tune it 7.5 KHz below or above the indicated channel. Use narrow band deviation up to 5 kHz without pre-emphasis, if possible. I suggest to use SDR, so check out the SDR page. Then enter the ID of your pager. You will find it printed on the device and/or on the 18 pin chip inside. If your pager's ID is 123456, enter it and press 'd' to start paging:
    on-hook: 123456 (press d=dial)
    mncc_console.c:358 info   : Outgoing call to '123456'
    call.c:699 info   : Received MNCC call from fixed network '' to mobile '123456'
    call.c:706 info   : Indicate MNCC call confirm towards fixed network
    call.c:717 info   : Outgoing call from '' to '123456'
    eurosignal.c:318 info   : Creating call instance to page ID '123456'.
    call.c:478 info   : Call has been answered by '123456'
    call.c:466 info   : Indicate MNCC answer towards fixed network
    mncc_console.c:206 info   : Call connected to '123456'
    eurosignal.c:605 info   : Station acknowledges, playing announcement.
    eurosignal.c:387 notice : Transmitting ID '123456'.
    eurosignal.c:387 notice : Transmitting ID '123456'.
    eurosignal.c:387 notice : Transmitting ID '123456'.
    eurosignal.c:387 notice : Transmitting ID '123456'.
    mncc_console.c:388 info   : Call hangup
    call.c:774 info   : Received MNCC release from fixed network with cause 16
    call.c:778 info   : Call released toward mobile network
    eurosignal.c:760 info   : Call has been disconnected by network.
In order to receive a paging message, use -R (--rx). Then the software will decode the received IDs and display them. You may also use both -R -T to allow the software to decode while it is encoding. You may append a station ID as command line option, so it is pre-selected and must not be typed in. You can also use digits like 'A', 'B', 'C', 'D' and 'E' to define Spare digits 1..5. I guess that these extension digis were never used, but it is supported by most pagers. Using a "Spare 2" as third digit looks like this:
    # src/eurosignal/eurosignal -k B 12B456
Make your own station ID ROM Sometimes you find a pager but the internal ROM with the station ID is missing. This is because there was no database (in the first place) to block unallocated / unsubcribed station IDs. Instead the ROM was removed from the pager when the subscriber unsubscribed the service. Learn how to build your own ROM from a few diodes: TeKaDe E 13-1 Bosch FRE 3 BBC ES-E1 Telefunken ES-5 ANT D 200 E SEL E299 Bosch FRE 2 SEL E300 Motorola E300 M Compur E300 ES SEL E300-1 Motorola E300-1 M Compur E300-1 ES Gundig FU 20 Storno CRP 3000 Dantronik DT 400 Grundig FU20.1 Storno CRP 3000.1 Dantronik DT 400.1 Multitone RPR 390 Telefunken ES 1/2 [Back to main page]