rs232 is the plug for inputs...rpm, tps, etc.
round connector goes to the display unit.
believe you need a display unit....unless you have the "basic" version that has a big red record button on the end with the round DIN connector. in that case the DIN connector is the comms port. i assume you have found the manuals at
https://store.traqmate.com/?
might be good to search the net or someone selling an entire system....should be cheap...they all are super old. to be blunt, the thing is fairly useless without a display unit. a lot of the value is the ability to see data in real time and change settings in the car.