Getting the Pro-Lite signs to work.
The instructions say to make a 4 conductor telephone cable to a 9 pin female serial connector. Red and Green go to pin 2 and 3 then the yellow wire goes to pin 5. Well I tried 300 baud, 9600 baud, a sign ID number of 1 to 10 and nothing worked. I reversed pins 2 and 3 to no avail. I got out my voltmeter and checked pins 2 and 3 and they were right to begin with. When they are wired correctly they should both meter about negative 2 to negative 5 volts. I also found out that both the yellow and the black wire are ground and can connect to pin 5 of the 9 pin serial connector.
There were two solutions to my dilemma. In spite of what the notes say both signs were configured to 2400 baud. I figured that out by trial and error. You are supposed to get a remote control and use that to find out what the baud rate and the sign ID is currently set to. However if you select a sign ID of ‘0’ it sends your message to ‘all’ or in this case ‘any’ sign that you have connected. Telling it to display the time is an easy way to test the communications setup. Once that is set you can move on to more advanced programming.