A base station transmits a continuous 2280 Hz idle tone on downlink channel.
A mobile station detects this tone and indicates a green light.
If the channel is busy or unused in that area, the green light does not appear.
The user must switch channel using the dial.
</p>
<center><imgsrc="a-netz-green.jpg"/></center>
<p>
2. Call from mobile station
<br><br>
The mobile station will only seize the channel, if the green light is on, otherwise it is blocked.
When the user picks up the handset, the phone switches on its transmitter on uplink channel and transmits a continous 1750 Hz calling tone.
The base station receives this tone and turns off its 2280 Hz idle tone.
The mobile station detects the tone is missing and turns off its 1750 calling tone.
The the speech path is connected through to an operator.
The operator asks for the mobile station number and the number to dial and places the call.
</p>
<p>
3. Call to mobile station
<br><br>
A caller calls the operator and tells the number and the location of the mobile station to reach.
The first 2 digits of the 7-digits mobile station number define on which channel the mobile station has to be paged.
(The user of the mobile station as well as the operator have a list of the calling channels for all base station.
This list shows which 2 digits refer to which channel in a particular area.
The user must select the right channel in order to get paged.)
<br><br>
The third digit of the mobile station number defines what groups of frequencies are used for paging the phone. For each of the last four digits there is a group. (Some digits use the same group.)
</p>
<p>
<ul>
<li>Number xx0xxxx: 2, 2, 3, 3
<li>Number xx1xxxx: 1, 1, 2, 2
<li>Number xx2xxxx: 1, 1, 3, 3
<li>Number xx3xxxx: 1, 1, 2, 3
<li>Number xx4xxxx: 1, 2, 2, 3
<li>Number xx5xxxx: 1, 2, 3, 3
<li>Number xx6xxxx: 1, 1, 1, 2
<li>Number xx7xxxx: 1, 1, 1, 3
<li>Number xx8xxxx: 2, 2, 2, 3
<li>Number xx9xxxx: 1, 2, 2, 2
</ul>
</p>
<p>
If a number is 2431790, the third digit ('3') tells us use group 1 for digits four and five, group 2 for digit six and group 3 for digit seven.
</p>
<p>
Group 1:
<ul>
<li>Digit 1: 352.5 Hz
<li>Digit 2: 367.5 Hz
<li>Digit 3: 382.5 Hz
<li>Digit 4: 397.5 Hz
<li>Digit 5: 412.5 Hz
<li>Digit 6: 427.5 Hz
<li>Digit 7: 442.5 Hz
<li>Digit 8: 457.5 Hz
<li>Digit 9: 472.5 Hz
<li>Digit 0: 487.5 Hz
</ul>
</p>
<p>
Group 2:
<ul>
<li>Digit 1: 502.5 Hz
<li>Digit 2: 517.5 Hz
<li>Digit 3: 532.5 Hz
<li>Digit 4: 547.5 Hz
<li>Digit 5: 562.5 Hz
<li>Digit 6: 577.5 Hz
<li>Digit 7: 592.5 Hz
<li>Digit 8: 607.5 Hz
<li>Digit 9: 622.5 Hz
<li>Digit 0: 637.5 Hz
</ul>
</p>
<p>
Group 3:
<ul>
<li>Digit 1: 652.5 Hz
<li>Digit 2: 667.5 Hz
<li>Digit 3: 682.5 Hz
<li>Digit 4: 697.5 Hz
<li>Digit 5: 712.5 Hz
<li>Digit 6: 727.5 Hz
<li>Digit 7: 742.5 Hz
<li>Digit 8: 757.5 Hz
<li>Digit 9: 772.5 Hz
<li>Digit 0: 787.5 Hz
</ul>
</p>
<p>
Because our 4th digit is 1, we find 352.5 Hz in group 1.
Because our 5th digit is 7, we find 442.5 Hz in group 1.
Because our 6th digit is 9, we find 622.5 Hz in group 2.
Because our 7th digit is 0, we find 787.5 Hz in group 3.
<br><br>
All these tones are sent simultaniously from the base station to the mobile startion.
The mobile stations has four detectors for the four frequencies.
If all four tones are detected by the mobile station, a yellow light and a buzzing sound is indicated.
There is no ringback indication from the mobile station to the base station.
When the user picks up the handset, the phone switches on its transmitter on uplink channel and transmits a continous 1750 Hz answer tone.
The base station receives this tone and turns off the four paging tones.
The mobile station detects the tone is missing and turns off its 1750 answer tone.
The the speech path is connected through to the caller (or operator).
</p>
<center><imgsrc="a-netz-yellow.jpg"/></center>
<p>
4. Release by the mobile station
<br><br>
If the user hangs up, the mobile station transmits a continous 1750 Hz release tone.
The base station receives this tone and disconnects the call. It transmits the continous 2280 Hz idle tone.
The mobile station receives this tone and turns off the transmitter.
</p>
<p>
5. Release by the base station
<br><br>
If the caller or the operator hangs up, the base station returns to idle. It transmits the continous 2280 Hz idle tone.
The mobile station receives this tone and turns off the transmitter.
In this case the level of each tone is two times highter (+3 dB), but the peak level is two times lower (-3 dB) than the peak level of 4 simultanious tones.
Be sure to check: Does your transmitter has enough frequency deviation (15 KHz is suggested)? Do you really send the correct number of your phone, check the frequencies of your phone and use "-D 0" option to see what 4 frequencies the base station actually transmits.