+
+
+
+ | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| VHF Low Band | ||
|---|---|---|
| Channel | Base (MHz) | Mobile (MHz) |
| ZO | 35.26 | 43.26 |
| ZF | 35.30 | 43.30 |
| ZM | 35.38 | 43.38 |
| ZH | 35.34 | 43.34 |
| ZA | 35.42 | 43.32 |
| ZY | 35.46 | 43.46 |
| ZR | 35.50 | 43.50 |
| ZB | 35.54 | 43.54 |
| ZW | 35.62 | 43.62 |
| ZL | 35.66 | 43.66 |
| VHF High Band | ||
|---|---|---|
| Channel | Base (MHz) | Mobile (MHz) |
| JJ | 152.48 | 157.74 (Canada only) |
| JL | 152.51 | 157.77 |
| YL | 152.54 | 157.80 |
| JP | 152.57 | 157.83 |
| YP | 152.60 | 157.86 |
| YJ | 152.63 | 157.89 |
| YK | 152.66 | 157.92 |
| JS | 152.69 | 157.95 |
| YS | 152.72 | 157.98 |
| YR | 152.75 | 158.01 |
| JK | 152.78 | 158.04 |
| JR | 152.81 | 158.07 |
| JW | 152.84 | 158.10 (Canada only) |
| UHF Band | ||
|---|---|---|
| Channel | Base (MHz) | Mobile (MHz) |
| QC | 454.375 | 459.375 |
| QJ | 454.40 | 459.40 |
| QD | 454.425 | 459.425 |
| QA | 454.45 | 459.45 |
| QE | 454.475 | 459.475 |
| QP | 454.50 | 459.50 |
| QK | 454.525 | 459.525 |
| QB | 454.55 | 459.55 |
| QO | 454.575 | 459.575 |
| QR | 454.60 | 459.60 |
| QY | 454.625 | 459.625 |
| QF | 454.65 | 459.65 |
+The modulation is FM. The frequency deviation of speech is 2500 Hz ??? at 1000 Hz. +Signaling tones have a frequency deviation of 5000 Hz. +Pre-Emphasis is used for speech only. +
+ ++Tones used for signaling: +
+ ++
| Base -> Mobile | |
|---|---|
| Idle | 2000 Hz |
| Seize | 1800 Hz |
+
| Mobile -> Base | |
|---|---|
| Guard | 2150 Hz |
| Connect | 1633 Hz |
| Disconnect | 1336 Hz |
+Idle State: +
+ ++All transceivers of a base station that are not in use, are turned off, except for one channel, the idle channel. +Only one channel being idle will transmit the 2000 Hz Idle tone and listens for the 2150 Hz Guard tone. +If the (only) channel with the Idle tone is seized by a mobile phone or the public telephone exchange, another channel, that is turned off, is activated and sends the Idle tone and becomes the new idle channel. +
+ ++When a mobile phone is idle, it will search for a radio channel with Idle tone and suitable quality. +The transmitter will be off while the phone listens to the Idle tone or an incoming call from the base station. +When the Idle tone disappears for about 250 ms ???, it will search for another idle channel. +
+ ++Call from mobile phone: +
+ ++When the user picks up the handset of the mobile phone, the phone will seize the channel, transmits ANI and receives dial tone. +
+ ++First, the mobile phone will turn on the transmitter and sends 350 ms of 2150 Hz Guard tone, followed by 50 ms of 1633 Hz Connect tone. +As soon as the Guard tone, followed by Connect tone is detected by the base station, it will turn off 2000 Hz Idle tone and transmit silence. +(Another channel that is turned off, will then transmit the 2000 Hz Idle tone.) +Note that the base station has to respond even before the 50 ms of the Connect tone is over. +The mobile phone must detect the silence from the base station before it is done sending the Connect tone. +(There are special requirements on SDR/soundcard setup to respond fast enough.) +The mobile phone then continues to send Guard tone and waits for the base station to respond with the 1800 Hz Seize tone. +Note that there seems to be no timeout in the mobile phone, waiting for Seize tone. +The base station sends 250 ms of the Seize tone. +
+ ++If the mobile phone receives the Seize tone, it will send the ANI sequence. +The ANI sequence consists of 190 ms of Guard tone, followed by 7 pulsed digits. +Each digit is formed by pulses consisting of 25 ms Mark tone and 25 ms of Space tone. +After the last pulse of each digit the mobile phone sends 190 ms of Space tone. +The Mark tone is transmitted as 1633 Hz Connect tone. +The Space tone is transmitted as silence, if the pulse number was odd. +The Space tone is transmitted as 2150 Hz Guard tone, if the pulse number was even. +The pulse number is counted from the first pulse of the first digit through the last pulse of the last digit. +The mobile phone will then through-connect speech path, the user awaits the dial tone. +
+ ++The base station verifies the received ANI and presents a dial tone or forwards the call to an operator. +
+ ++When a number is dialed from a mobile phone, Guard tone is sent continuously as soon a the dial goes off normal (when the dial is moved from its resting position), which should be about 400 ms ???. +Each digit is formed by pulses consisting of 60 ms Mark tone and 40 ms of Space tone. +The Mark tone is transmitted as 1633 Hz Connect tone. +The Space tone is transmitted as 2150 Hz Guard tone. +The Space tone continues until the dial returned to normal, which should be about 200 ms ???. +
+ ++Call towards mobile phone: +
+ ++The land user dials the phone number of the mobile phone. +It consists of the 3 digit area code and the 4 digit suffix. +The 3 digit prefix (mobile exchange) is omitted when paging the mobile phone. +
+ ++First, the base station selects the idle channel that is transmitting the 2000 Hz Idle tone. +(Another channel that is turned off, will then transmit the 2000 Hz Idle tone.) +If there is no channel available, the land user receives a busy signal. +The 7 digit number is transmitted towards the mobile phone via alternating tones. +The base station transmits a 1800 Hz Seize tone for about 400 ms (???) before, between and after each digit. +Each digit is formed by pulses consisting of 50 ms Mark tone and 50 ms of Space tone. +The Mark tone is transmitted as 2000 Hz Idle tone. +The Space tone is transmitted as 1800 Hz Seize tone. +The base station will start timer for 3 to 4 seconds waiting for the mobile phone to respond with a 2150 Hz Guard tone. +
+ ++If the mobile phone receives digits from base station, it compares the digits with its own number. +If the number does not match, it will abort and scan for the idle channel. +If the number matches the mobile phone will transmit the Guard tone up to 750 ms, waiting for the ringing sequence. +After sending Guard tone, the mobile phone will ring and wait for answer. +
+ ++If the base station does not receive the Guard tone from the mobile phone, it will return to idle state. +The land user will receive an announcement that the called phone is not available at this moment. +If the base station receives the Guard tone from the mobile phone, it will send a ringing sequence for about 45 seconds. +Ringing by the base station is composed of 1800 Hz Seize tone and 2000 Hz Idle tone, each alternating after 25 ms for 2 seconds, then 4 seconds of Seize tone. +
+ ++The mobile phone rings the bell using the tones received from the base station. +If the 1800 Hz Seize tone disappears, the phone stops ringing and returns to idle channel. +
+ ++If the user of the mobile phone answers, the mobile phone transmits 1633 Hz Connect tone for 400 ms and through-connects speech path. +
+ ++If the base station receives the Connect tone, it will stop the ringing sequence, answers the call from the land user and through-connect the speech path. +
+ + ++Release by the mobile phone: +
+ ++If the mobile user hangs up, the mobile phone starts the release sequence by sending alternating 1336 Hz Release tone and 2150 Hz Guard tone, 25 ms each. +After 750 ms sending that sequence, the mobile phone turns off transmitter and searches for idle channel. +
+ ++When the base station receives the release sequence, it will return to idle state. +
+ + ++Release by the base station: +
+ ++When the mobile phone is ringing, it will stop if the base station removes the ringing sequence. +There is no release sequence to release an a active call towards mobile phone. +
+ + + ++Base station in Idle state: +
+ ++The base station uses a 600 Hz tone to indicate an idle channel. +Similarly to the IMTS, only one idle channel send the 600 Hz tone, the other channels are turned off. +
+ ++Call from mobile phone +
+ ++The mobile station does not send any signaling tone at all. +The radio signal is used to start a call. +Whenever the user picks up the phone and presses the push-to-talk button, a connection is made to an operator. +The operation is half duplex, so there is no release by stopping transmission of the mobile phone. +The operator has to terminate the call. +
+ ++Call from base station +
+ ++To page a mobile phone, the operator has to dial the 5 digits of the mobile phone. +The operator has to add the digit '1' in front of the 5 digit subscriber ID. +This digit is used to reset the paging detector inside mobile phone. +Note that the subscriber ID must not have a digit '1'. +Each pulse from the base station is a transition from 600 Hz to 1500 Hz or from 1500 Hz to 600 Hz. +Two or more pulses are separated 100 ms. +Each digit is separated 400 ms ???. +After the last pulse of the last digit, the tone sustains until the caller hangs up. +The mobile phone rings. +To answer the call, the user presses the push-to-talk button. +The ringing can be released by sending another transition pulse or by removing the tone for a short time. (This is for further study.) +
+ ++ +Setup of an IMTS base station +
+ ++Find out what band and channels your phone supports. Then get a list of all available bands and channels: +
+ ++ +# src/imts/imts -k list + ++ +
+Assume the phone supports VHF Low band, so we select channel 'YK' with the command line option '-k YK', or select any other channel your phone supports. +In order to have a low latency, you must add '-b 5' to the command line option. +Then tune the transmitter to the indicated channel and receiver to the other indicated channel. +Transmit with a normal loud speech volume, but not too loud. +The actual level is not yet relevant. +
+ ++ +# src/imts/imts -k YK -b 5 +... +imts.c:381 info : Entering IDLE state on channel YK, sending 2000 Hz tone. +imts.c:336 notice : Created channel #YK +Base station on channel YK ready, please tune transmitter to 152.660 MHz and receiver to 157.920 MHz. (-5.260 MHz offset) +on-hook: ....... (enter digits 0..9) + ++ + +
+If you receive permanent buffer underruns, see 'Fast Seize' below. +Power on your phone. +Be sure to use attenuator on the antenna, so it will not transmit full 25 Watts close to your receiver equipment. +The phone should search and stop at the selected channel. +If the phone does not support automatic channel selection, select channel YK manually. +
+ ++Now pick up the handset of your phone and it should transmit the Guard tone, followed by a short Connect tone. +If the phone does not lock or does not transmit, check if your transmitter transmits the Idle tone. +If the phone transmits, your base station should respond to the seize sequence by the phone and the phone transmits ANI towards your base station. +
+ ++ +# src/imts/imts -k YK -b 5 +... +imts.c:381 info : Entering IDLE state on channel YK, sending 2000 Hz tone. +imts.c:336 notice : Created channel #YK +Base station on channel YK ready, please tune transmitter to 152.660 MHz and receiver to 157.920 MHz. (-5.260 MHz offset) +imts.c:886 notice : Received Guard tone, turning off IDLE tone +imts.c:544 info : Received seize (Guard + Connect tone) from mobile phone. +imts.c:545 info : -> Guard tone duration: 350 ms (level 69%) +imts.c:408 info : All channels are busy now, cannot activate any other channel. +imts.c:907 notice : Sending Seize to mobile phone. +imts.c:784 info : Received ANI digit '2' from mobile phone (level 71%). +imts.c:784 info : Received ANI digit '1' from mobile phone (level 77%). +imts.c:784 info : Received ANI digit '6' from mobile phone (level 77%). +imts.c:784 info : Received ANI digit '2' from mobile phone (level 77%). +imts.c:784 info : Received ANI digit '6' from mobile phone (level 77%). +imts.c:784 info : Received ANI digit '3' from mobile phone (level 71%). +imts.c:784 info : Received ANI digit '0' from mobile phone (level 71%). +imts.c:790 info : ANI '2162630' complete, sending dial tone. + ++ +
+If the base station does not receive Guard tone or receives bad ANI digits, check the receiver and the receive level. +To test the receiver side, tune the receiver to the frequency of the transmitter and check the loopback signal. Adjust your receiver (sound card input) to match about 100% level: +
+ ++ +... +imts.c:876 notice : Received idle tone (level of 97%), loopback? +imts.c:876 notice : Received idle tone (level of 97%), loopback? +imts.c:876 notice : Received idle tone (level of 97%), loopback? +imts.c:876 notice : Received idle tone (level of 97%), loopback? +... + ++ +
+Return your receiver to the uplink frequency and try to make a call again. +If it works, use you dial pad (or rotary dial) to dial the number. +
+ ++To call towards mobile station, enter the 7 digit mobile station ID on your keyboard or add it to the command line. +Use the same phone number you received with the ANI above, this is your mobile station ID. +Then press 'd' to page and ring the phone: +
+ ++ +... +mncc_console.c:358 info : Outgoing call to '2162630' +call.c:699 info : Received MNCC call from fixed network '' to mobile '2162630' +call.c:706 info : Indicate MNCC call confirm towards fixed network +call.c:717 info : Outgoing call from '' to '2162630' +imts.c:1176 info : Call to mobile station, paging number: 2162630 +imts.c:445 info : Entering paging state, sending phone's ID '2162630'. +imts.c:408 info : All channels are busy now, cannot activate any other channel. +imts.c:942 info : Sending paging digit '2' as pulses. +imts.c:942 info : Sending paging digit '1' as pulses. +imts.c:942 info : Sending paging digit '6' as pulses. +imts.c:942 info : Sending paging digit '2' as pulses. +imts.c:942 info : Sending paging digit '6' as pulses. +imts.c:942 info : Sending paging digit '3' as pulses. +imts.c:942 info : Sending paging digit '0' as pulses. +imts.c:755 info : Received acknowledge (Guard tone) from mobile phone (level 71%). +call.c:440 info : Call is alerting +call.c:428 info : Indicate MNCC alerting towards fixed network +mncc_console.c:202 info : Call alerting +imts.c:466 info : Received response from mobile phone, ringing. +imts.c:1013 info : Sending ringing signal as pulses. +imts.c:1022 info : Sending pause after ringing. +imts.c:1013 info : Sending ringing signal as pulses. +imts.c:1022 info : Sending pause after ringing. +imts.c:763 info : Received answer (Connect tone) from mobile phone (level 75%). +call.c:478 info : Call has been answered by '2162630' +call.c:466 info : Indicate MNCC answer towards fixed network +mncc_console.c:206 info : Call connected to '2162630' +imts.c:476 info : Received answer from mobile phone, conversation started. + ++ +
+To disconnect a call, the phone must be hung up: +
+ ++ +... +imts.c:654 info : Received disconnect sequence from mobile phone (level 90%). +imts.c:418 info : Turing transmitter off. +imts.c:381 info : Entering IDLE state on channel YK, sending 2000 Hz tone. + ++ +
+Level adjustment: +
+ ++Don't care about it, if you use SDR, since levels are always correctly modulated. +Now it is time to actually care about the correct transmit and received level. +In the example above you see a level around 70..77%. +Now tune your receiver to your transmitter frequency again. +Adjust the level to something around 73% using a variable resistor on my soundcard's input. (+- 10% is good) +
+ ++ +... +imts.c:876 notice : Received idle tone (level of 88%), loopback? +imts.c:876 notice : Received idle tone (level of 76%), loopback? +imts.c:876 notice : Received idle tone (level of 73%), loopback? +imts.c:876 notice : Received idle tone (level of 73%), loopback? +imts.c:876 notice : Received idle tone (level of 73%), loopback? +imts.c:876 notice : Received idle tone (level of 73%), loopback? +... + ++ +
+Now, whatever frequency deviation the phone transmits for signaling, so does your base station. (Around 73% in this case.) +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 see the result from your phone. (You should now receive the phone at around 100%.) +
+ ++Pre- and De-Emphasis: +
+ ++In order to have correct level of signaling tones, your transmitter and your receiver should not use pre- and de-emphasis. +Let this software do that instead, then the signaling tones do not use pre-emphasis, just the voice. +If possible, add command line option '-p' for pre-emphasis of the transmit signal and '-d' for de-ephasis of the received signal. +Don't care about it, if you use SDR, since pre-emphasis and de-emphasis is automatically selected and used. +
+ ++Fast seize detection: +
+ ++Sometimes your sound device might not be fast enough to handle a small sound buffer. +The maximum buffer of 5 ms (command line option '-b 5') might cause repeating trouble: +
+ ++ +sound_alsa.c:458 error : Buffer underrun: Please use higher latency and enable real time scheduling +sound_alsa.c:127 error : cannot prepare audio interface for use (Device or resource busy) +sender.c:330 error : Failed to get number of samples in buffer (rc = -32)! +sender.c:338 error : Trying to recover! + ++ +
+ +We must not increase buffer, because we would detect the Connect tone too late, so we would respond too late. +We must respond before we detect the Connect tone, so that our response matches the time the Connect tone is actually transmitted by the phone. + +
+ ++To do this we must measure the length of the Guard tone. +First pick up the phone and remember the Guard tone duration. +It should be close to 350 ms. +
+ ++ +imts.c:544 info : Received seize (Guard + Connect tone) from mobile phone. +imts.c:545 info : -> Guard tone duration: 349 ms (level 99%) + ++ +
+Now put the base station into loopback mode and tune receiver to transmitter or loop soundcard's output to input. +
+ ++ +# src/imts/imts -k YK -l 2 +... +imts.c:942 info : Sending paging digit '1' as pulses. +imts.c:861 info : Received paging test digit '1' (level 103% delay 68 ms). +imts.c:942 info : Sending paging digit '2' as pulses. +imts.c:861 info : Received paging test digit '2' (level 103% delay 67 ms). +imts.c:942 info : Sending paging digit '3' as pulses. +imts.c:861 info : Received paging test digit '3' (level 103% delay 67 ms). + ++ +
+In this case the soundcard's round trip delay is 67 ms. +Substract 67 from 349 and you get 282. +Add '-F 282' to command line option, instead of '-b 5'. +Now we react about 282 ms after we detected the start of the Guard tone. +The reaction now matches the time when the phone transmits the Connect tone. +(Tested with a Limermore LAP-2000 phone.) +
+ ++Detecting loss of carrier signal: +
+ ++This works with SDR only, because we do not have any RSSI (Received Signal Strength Indicator) signal from a radio connected to the sound card. +With SDR we know the RX level, so we can define a threshold value for a lost signal. +Use '-S <db>' or '--squelch <db>' to define the squelch threshold level. +To measure the noise floor, use the 'm' key to get a bar graph of the current RSSI. (RF level) +Add some dB to the noise floor for the squelch threshold value. +An easier way is to use '-S auto' or '--squelch auto' to automatically measure the noise floor level and then automatically use a threshold level that is some dB above this measured level. +This level is then used to detect loss of carrier. +Also this level is used to mute the audio path, whenever the signal gets lost for a short time. +After about 12 seconds of signal loss, a call is released. +
+ ++... +squelch.c:94 info : RF signal measurement: -69.2 dB noise floor, using threshold of -63.2 dB +... ++ +
+In the following example I cut off the power of the phone being in a call and waited 12 seconds for the base station to time out: +
+ ++... +squelch.c:114 info : RF signal weak: Muting audio (RF -77.6 dB < -70.7 db) +imts.c:491 notice : Detected loss of signal after 12 seconds, releasing. +... ++ +
+ +Setup of an MTS base station +
+ ++To detect an outgoing call or answer from a mobile phone, it is required to use squelch. +Squelch is only available with SDR support. +The command line option '-M' is used to switch to MTS mode. +Also we use loopback mode '-l 2' to test RF loopback. +Alternatively use '-l 1' to perform an internal loopback. +The following example shows setup with LimeSDR (not LimeSDR mini!): +
+ ++ +# src/imts/imts --limesdr -k JS -M -l 2 +... +imts.c:443 info : Entering paging test state, sending digits 1234567890. +imts.c:408 info : All channels are busy now, cannot activate any other channel. +imts.c:336 notice : Created channel #JS +Base station on channel JS ready, please tune transmitter to 152.690 MHz and receiver to 157.950 MHz. (-5.260 MHz offset) +... +imts.c:861 info : Received paging test digit '1' (level 98% delay 9139 ms). +imts.c:992 info : Sending paging digit '1' as pulses. +imts.c:861 info : Received paging test digit '1' (level 100% delay 80 ms). +imts.c:992 info : Sending paging digit '2' as pulses. +imts.c:861 info : Received paging test digit '2' (level 100% delay 78 ms). +imts.c:992 info : Sending paging digit '3' as pulses. +imts.c:861 info : Received paging test digit '3' (level 100% delay 77 ms). +imts.c:992 info : Sending paging digit '4' as pulses. +imts.c:861 info : Received paging test digit '4' (level 100% delay 78 ms). +imts.c:992 info : Sending paging digit '5' as pulses. +imts.c:861 info : Received paging test digit '5' (level 100% delay 77 ms). +imts.c:992 info : Sending paging digit '6' as pulses. +... + ++ +
+Now run the base station without loopback. +Add "-S auto" to use squelch level with automatic level calibration. +Be sure to have an attenuator, so you do not saturate your input of your SDR. +Refer to the SDR help page for more information and input level display. +The following example shows a call from mobile phone, just by transmitting toward base station: +
+ ++ +# src/imts/imts --limesdr -k JS -M -S auto +... +squelch.c:61 info : RF signal squelch: Use automatic threshold +imts.c:386 info : Entering IDLE state on channel JS, sending 600 Hz tone. +imts.c:336 notice : Created channel #JS +Base station on channel JS ready, please tune transmitter to 152.690 MHz and receiver to 157.950 MHz. (-5.260 MHz offset) +... +dsp.c:466 info : Low RF level, muting. +squelch.c:99 info : RF signal measurement: -69.9 dB noise floor, using squelch threshold of -59.9 dB +squelch.c:99 info : RF signal measurement: -70.2 dB noise floor, using squelch threshold of -60.2 dB +squelch.c:112 info : RF signal strong: Unmuting audio (RF -54.2 >= -60.2 dB) +dsp.c:476 info : High RF level, unmuting; turning transmitter on. +imts.c:506 info : Detectes RF signal in IDLE mode, calling the opterator at '010'. +call.c:405 info : Incoming call from 'unknown' to '010' +call.c:407 info : -> Call to Operator '010' +call.c:385 info : Indicate MNCC setup towards fixed network +mncc_console.c:165 info : Incoming call from '' +mncc_console.c:196 info : Call automatically answered +call.c:744 info : Received MNCC answer from fixed network +call.c:746 info : Call answered +call.c:748 info : Indicate MNCC setup complete towards fixed network + ++ +
+To terminate the call, press 'h': +
+ ++ +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 +imts.c:1237 info : Call has been released by network, releasing call. +imts.c:1254 notice : Outgoing release, during call, releasing! +imts.c:418 info : Turing transmitter off. +imts.c:386 info : Entering IDLE state on channel JS, sending 600 Hz tone. + ++ +
+To call the mobile phone, enter the number as command line parameter or after running the base station. +Then press 'd' to dial the number. +If the phone rings, answer by start transmitting: +
+ ++ +on-hook: 23042 (press d=dial) +mncc_console.c:358 info : Outgoing call to '23042' +call.c:699 info : Received MNCC call from fixed network '' to mobile '23042' +call.c:706 info : Indicate MNCC call confirm towards fixed network +call.c:717 info : Outgoing call from '' to '23042' +imts.c:1177 info : Call to mobile station, paging number: 23042 +imts.c:445 info : Entering paging state, sending phone's ID '23042'. +imts.c:408 info : All channels are busy now, cannot activate any other channel. +imts.c:992 info : Sending paging digit '2' as pulses. +imts.c:992 info : Sending paging digit '3' as pulses. +imts.c:992 info : Sending paging digit '0' as pulses. +imts.c:992 info : Sending paging digit '4' as pulses. +imts.c:992 info : Sending paging digit '2' as pulses. +imts.c:975 info : Digits complete, assuming the phone is ringing. +call.c:440 info : Call is alerting +call.c:428 info : Indicate MNCC alerting towards fixed network +mncc_console.c:202 info : Call alerting +... +squelch.c:112 info : RF signal strong: Unmuting audio (RF -66.5 &g6;= -67.7 dB) +dsp.c:476 info : High RF level, unmuting. +imts.c:520 info : Detected RF signal, mobile is now transmitting. +call.c:478 info : Call has been answered by '23042' +call.c:466 info : Indicate MNCC answer towards fixed network +mncc_console.c:206 info : Call connected to '23042' +imts.c:476 info : Received answer from mobile phone, conversation started. + ++ +
+Use MTS with 7 digit ID or IMTS with 5 digit ID: +
+ ++Some later phone allow to operate in IMTS and MTS networks. +In order to roam, the caller ID length can be different. +Use command line option '-5' to use IMTS mode with 5 digit IDs. +Use command line option '-7' to use MTS mode with 7 digit IDs. +
+ ++
