how determine type unknown connection?

hi
I have a device that has a communication port but I do not know which type of connection. I've measured the voltages on pins , that The following values were obtained :


in your opinion , this is which connection??how can determine type connection ?
in The manufacturer's catalog Been picture following :


Also come in the catalog the following descriptions :

Looks like a dongle to provide electrical isolation between the host and your device, but I could be wrong.

Is the data supposed to be unidirectional?

ard said:

Looks like a dongle to provide electrical isolation between the host and your device

Click to expand...

i use isolated RS232 as below link between them but dont work !
**broken link removed**

ard said:

Is the data supposed to be unidirectional?

Click to expand...

no , it is bidirectional

i have a Transducer from Manufacturer that Operates properly .
Is there a way that determine type connection with this Transducer ??

for more detail :
I get below voltage in run time on each pin :
top and bottom pin are nearly 3.5 volt and Remain at the same level when pc and device exchange data together .
left pin become nearly -4.92 volt in connect time and change when pc and device exchange data together (for example become -0.8 or -2.3 or -3.2 and then return to -4.92 when pc and device do not exchange data together )
and voltages after Manufacturer Transducer are following :
voltage on rxd pin is -4.9 volt in connect time and Remain at the same level when pc and device exchange data together .
voltage on txd pin is -2.9 volt in connect time and change when pc and device exchange data together (for example become 2.4 or 1.8 or -0.4 and then return to -2.9 when pc and device do not exchange data together )