3Com VCX V7122 SIP VoIP Gateway User Manual 141For example: To configure the dial tone to 440 Hz only, define the following text:Figure 57 Defining a Dial Tone Example#Dial tone[CALL PROGRESS TONE #1]Tone Type=1Low Freq [Hz]=440High Freq [Hz]=0Low Freq Level [-dBm]=10 (-10 dBm)High Freq Level [-dBm]=32 (use 32 only if a single tone is required)First Signal On Time [10msec]=300; the dial tone is detected after 3 secFirst Signal Off Time [10msec]=0Second Signal On Time [10msec]=0Second Signal Off Time [10msec]=0Prerecorded Tones (PRT) FileThe Call Progress Tones mechanism has several limitations, such as a limited number ofpredefined tones and a limited number of frequency integrations in one tone. To work aroundthese limitations and provide tone generation capability that is more flexible, the PRT file canbe used. If a specific prerecorded tone exists in the PRT file, it takes precedence over thesame tone that exists in the CPT file and is played instead of it.Note that the prerecorded tones are used only for generation of tones. Detection of tones isperformed according to the CPT file.PRT File FormatThe PRT dat file contains a set of prerecorded tones to be played by the VCX V7122 duringoperation. Up to 40 tones can be stored in a single file. The prerecorded tones (raw dataPCM or L8 files) are prepared offline using standard recording utilities (such as CoolEdit TM)and combined into a single file using the TrunkPack Downloadable Conversion utility (seeCreating a Loadable Prerecorded Tones File on page 224).The raw data files must be recorded with the following characteristics: Coders: G.711 A-law, G.711 μ-law or Linear PCM Rate: 8 kHz Resolution: 8-bit Channels: monoThe generated PRT file can then be loaded to the VCX V7122 using the BootP/TFTP utility(see Configuration Files Parameters on page137) or via the Embedded Web Server (seeAuxiliary Files on page 86).The maximum size of the combined PRT file that can be stored in RAM is 1 MB. The PRTfile is permanently stored in flash memory only if there is available space. Otherwise, itshould be loaded (using the BootP/TFTP utility) each time the VCX V7122 is reset.The prerecorded tones are played repeatedly. This enables you to record only part of thetone and play it for the full duration. For example, if a tone has a cadence of 2 seconds onand 4 seconds off, the recorded file should contain only these 6 seconds. The PRT modulerepeatedly plays this cadence for the configured duration. Similarly, a continuous tone canbe played by repeating only part of it.
