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From: Eric.Bohlman@p1.f778.n115.z1.fidonet.org (Eric Bohlman)
Newsgroups: misc.handicap
Subject: Synthesizer interfacing
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Date: 19 Sep 90 02:10:56 GMT
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Index Number: 10458

[This is from the Blink Talk Conference]

Synthesizers, like modems, come in both internal and external varieties.   
External synthesizers connect to the computer via a serial port or, less  
commonly, a parallel port.  An external synthesizer will speak whatever is  
sent to it over the port.  Some of them will remain silent until you send a  
carriage return; in this respect they're more like printers than modems.   
Another similarity to printers is that they have various special codes to  
change pitch, speech rate and the like, just as printers have codes to change  
fonts and character spacing.

Internal synthesizers are cards that occupy various port addresses.  Unlike  
external synthesizers, they don't usually have their own processors to do  
text-to-speech conversion; rather, they rely on a memory-resident program to  
do the translation.  This program receives text and converts it to phonetic  
codes which are then sent to the synthesizer board.  The driver programs have  
a variety of ways of receiving text.  Some of them hook into the BIOS routines  
for dealing with serial or parallel ports.  With one of those, you just output  
text to the appropriate "port" as you would with an external unit.  Others  
(the Artic boards, for example) have their own software interrupt; you  
communicate with them by issuing a software interrupt, usually with some  
register pointing to the text you want them to speak.

Don't confuse the driver programs I mentioned with screen reader programs.   
The driver program simply does the text-to-speech translation for other  
programs that want to talk to the synthesizer; it doesn't automatically make  
screen output talk or keys echo.  That's a function of the screen reader.
 

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