I have a device that uses wired communication and need to decode it, however, I don't know anything about the protocol. I've never done this before (attempted to decode data where I don't know the protocol) and I'm hoping someone can give me some pointers as to the most efficient method to figure it out.

Here is what I know:

1. It's for a little league football scoreboard.
2. It travels about 300 feet.
3. It's wired and there are two wires going to the scoreboard.
4. When I measured the wires with a DMM it is about 14.9 VDC.
5. The data appears to be PWM as data is constantly flowing whether a button is pushed or not.
6. The frequency appears to be approximately 1.6 kHZ and I can see the data using an oscilloscope.
7. There are a lot of 74HCxx's on the PCB.
8. I tried using hyperterminal and while I could see data nothing appeared to be valid data. The speed does appear to be around 4800 bps.
9. There is an RJ11 jack on the PCB but I don't know if this is used for the communication or not. I was taking measurements from another connector on the PCB.

That's pretty much all I know. This is an area where I have very little experience (data communication) so any pointers would be appreciated.