ttl test program not working (case 10436)

[ARLUser]

I have a serial cable plugged into the 9 pin serial port of the computer. I have attached an led across pin 5 signal ground and pin 4 DTR. The led is off. Now at a dos command prompt I type echo sssssssssssss... > com1 and hit enter my led will stay lit for the duration of the string. My goal is to have RT send an echo pulse to the com port with variable time duration that is triggered by a stimulus tone being presented to the subject. By the way the led is direct connect to the serial port - no limiting resistors.