Question about cat and echo

Hello,
I am trying to send text to a USB to serial adaptor and then to an external speech synthesizer. I tried using the cat and echo commands with no luck. I have gotten some audio output from my synthesizer using Kermit a terminal emulator, so I am pretty sure my synthesizer and my USB to serial adaptor and the adaptors driver are all working. I want to send text to my synthesizer using the cat and or echo command. So my question is do I need to set something up in order to send text to my synthesizer, with the cat or echo command, and have audio output from my synthesizer? btw I know about VoiceOver.

how about the say command? typing say and then the text you want spoken will cause the computer to say what you wrote. you could always have it read from a file and pipe that to the say command too, like

cat textfile.txt |say