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MPTP | MPTP commands 12

3. MESSAGE CONSTRUCTION AND INTERPRETATION

As mentioned earlier, MPTP messages are sent between parties as specially formatted SMS messages.

The standard 7-bit GSM character set is used (cf. GSM 7-bit default alphabet table.pdf).

Most MPTP messages are sent in a semi-readable ASCII format and can thus be received and read using

any SMS enabled mobile phone. However, manually interpreting the data content of an MPTP message is

rather tedious, so the receiving instrument should be equipped with software for reacting to the messages

and their data content appropriately.

Some of the messages are partly binary and Base64 encoded (cf. 3.6) so that more data can be fitted into

one message.

Unlike other MPTP messages, AGPS (Assisted GPS) messages are always sent in unreadable binary

format. The instrument receiving such a message always needs to have suitable software for interpreting

them properly. Binary AGPS messages are treated in MPTP AGPS messages.pdf.

The later sections of this document list all MPTP commands. For each command, its usage and format is

given, along with a list of the Benefon or TWIG instruments which are equipped with software for using the

command in question.

3.1. Common fields

As mentioned above, most of MPTP messages sent in ASCII format is a semi-readable string, like the

example below:

!TRG_01/01_4_1_norm_075%_gps_2_N68.28.43,9_E027.27.02,4_37_

08.07.2003_17:44:23_081km/h_114deg_81

(For the curious, the above command is sent by a tracking process with a trigger for sending messages

when the speed limit of 81 km/h is exceeded.)

An MPTP command consists of a number of fields with different meanings. The fields can be found by

looking for field separator characters which separate them; the underscore character (_, Unicode 0x5F) is

used for this purpose. Note that the underscore character should not be used at middle of any string fields.

It should also be noted that the data in the command is case sensitive, so care should be taken to use

uppercase and lowercase letters as described in this document.

Some fields are common to several MPTP commands while others are specific to a command type. The

following table uses the sample command above for describing some fields commonly used in several

MPTP command types.

Field Description

!TRG

Command

A unique string of three to four characters which identifies the purpose of the

command and tells how the rest of it should be read. Note that these

characters should always be written with capital letters.

The first character of the command is by default a question mark or an

exclamation mark. The former (?) identifies the role of the sender of the

message as a Control Centre, while the latter (!) identifies it as a Mobile

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Benefon TWIG INBOX Manuale Utente Pagina 12