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.
Then start the base station using '-L 2' option for loop-back and tune receiver to the transmitter.
The base station generates a 1750 Hz test signal, just like the mobile phone.
Use the variable resistor (connecting your transmitter) to adjust the volume until the received level matches the same level of your previously received signal.
In my case I adjust the transmitter to match around 140%. (+- 10% is good)
Now, whatever frequency deviation the mobile phone transmits at 1750 Hz, so does your base station.
Use the other variable resistor (connecting your receiver) to adjust the volume until the level matches about 100%. (+- 10% is good)
Switch back the receiver to up-link frequency and restart the phone.
In this case the deviation level of each tone is two times higher (+6 dB). (The level transmitted is two times lower (-6 dB) than the peak level of 4 simultaneous tones. This may help transmitters with deviation limiters to make the phone ring.)
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.