Using cat and echo

Tried

cat > /dev/tty.usbserial-FTKVMAFF

still no audio output

I have suscribed to a screen reader mailing list, and members of the mailing list, had advised me to use cat and echo to test my synthesizer. Although one member of the mailing list did say that even though her synthesizer was working with her screen reader, it didn't work with echo. Another member of the mailing list said they had a traditional serial port, and they always got audio output from cat and echo?

I tried

cat > /dev/**.usbserial-FTKVMAFF
hello world

and then hit return(no audio output) then I typed cntrl-c to exit cat. I then tried

cat > /dev/tty.usbserial-FTKVMAFF
hello world

and then hit return(no audio output) then I typed cntrl-c to exit cat. I have been able to send a text file to my synthesizer, using a terminal emulator called ckermit. Within ckermit I used the transmit command to send a text file to my synthesizer. And from what I remember depending on how the file was saved i.e. plain text, rtf etc. effected the success of the transmit command. But people from the screen reader mailing list did suggest using echo and cat to test my synthesizer. Thanks for the responses.

ok
someone from the mailing list had told me, that the only reason he thought the cat and echo commands weren't working was because my synthesizer might need special control characters either at the beginning or end of the file, or in the case of cat at the beginning or end of the text , I am sending it. I did read in the user manual of my doubletalk speech synthesizer, that if you start a file with cntrl-A, the synthesizer will not speak what is immediatly after the cntrl-A, but treat it as a command. Like you can change the voice of the synthesizer with certain commands. I was testing out my synthesizer with ckermit(a terminal emulator) and when I would send a file, using ckermits transmit command, that started with cntrl-A, my synthesizer wouldn't speak immediatly. I would then send a file to my synthesizer that did not start with cntrl-A and my synthesizer would speak both files. Is it possible that cat is sending the text I write to the buffer? And my synthesizer is expecting a cntrl character and won't speak until it gets it? I do have a file on my computer, that starts with cntrl-A, then has some text, and ends with a NUL character. When I transmit that command, my synthesizer speaks in a different immediately. Does anyone know how to write a NUL character in terminal? I want to test the cat command by typing some text, and ending with a NUL character, and then hitting return.

ok
I found out why cat and echo weren't working. I sent some text, using the cat command, to my synthesizer and ended the text with a NUL character. By typing cntrl shift @. And my synthesizer spoke the text I had written. My question now is can I have cat append a file, or text with a NUL character automatically? So that when i use the ckermit log session command along with cat my synthesizer will speak the complete session, like if I type ls my synthesizer will speak the complete directory listing? Any help?