Modem - The use of standard voice modem (33.6kbps and above ) obviates the need for additional hardware for IVRS. The modem has a micro controller and a data pump (analog to digital to analogue converter). These two makes a beautiful voice /fax/ data interface to telephone line which can play voice files up sampling rate of 11025 bytes/sec (most commercial card allow up to 7200 byts/sec only) . Beside this you can divert your voice signal to / from internal speaker and microphone, and add external speaker and microphone. The PC communicates to Modem via serial port and AT commands. The complete AT command set contains more than 100 commands and available on net. The new voice modem has ability to read the CallerID information, receive/send fax , dial another number, line quality diagnosis etc. Due to use of modem , this IVRS is limited to two channel (or Telephone lines), because PC has only two serial ports. Multi port serial card can be installed but I have not tested it. In my opinion this not a limitations as one modem can cater to almost 3000 user. I have seen other IVRS which uses Dialogic Cards, these cards are nothing but the multiple modem (2, 4, 8, 16 ) on ISA or PCI cards. As these card communicates with PC via ISA or PCI slot, the data transfer speed is very high and hence PC can cater to multiple modem (8 or 16) at a time. How ever cost of these card is prohibitive and around Rs.35,000 for a two channel card. (when last I checked).
Voice files -
There is lot of reading material for sound file on the net. I will restrict
this discussion to IVRS only. The modem understands only rmd (raw modem
data) files. The pvftools (Portable Voice Format Tools) which
is included with Vgetty has excellent utilities to convert files from one
format to another format. I have used two types of files ( in sfiles/ of
this package), one is raw modem data type which can be sent directly to
modem for playing and another is lin type. In any IVRS to play smoothly
messages ,numbers, the messages have to be created on the fly.
This is where another type of file called lin is use full. These are nothing
but the voice data files with no header or footer. You can cut and paste
these file to make a new file. This lin file is converted to raw modem
data type and then played to modem. The lin and rmd files can be
created from wave (mono) using pvftools, I have used and included some
pvftools with this distribution. The voice files with this distribution
are customized for Rockwell chip set modem, which is most popular. The
pvftools supports other modem type also also. I have tested Dlink,
GVC, LanBit and many other modem. The modem speed does not matter because
voice modem with 33.6 Kbps and above will work fine.
Adaptability - This distribution is complete with all the voice files and to make a full functional IVRS you need a few line of perl scripts and additional message files. You may need to record messages, if you want additional messages or you do not like the tone of these files, and cut them in to separate file. These messages can be recorded in wav format then converted to rmd or lin format. File convert utilities are also included with distribution. You also need to write small scripts to fetch the numerical data from files which is played to caller. The demo scripts included in this distribution gives fair knowledge of module.
Copyright (C) 2001, Mukund Deshmukh. All rights reserved. This program is free software, you can redistribute it and/or modify it under the same terms as Perl itself.
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