I cannot find any user/wiring diagram info regarding your Koss T/10A anywhere online, therefore I suggest the following options:
1. Disassemble the Koss T/10A and use an Ohmmeter to help you to draw the circuit details down so that you know where each of the 7 wires goes to in the unit so you will then know what their function is. This will help you to connect it to your receiver.
2. Disassemble the Koss T/10A and take several close up photographs of the inside showing as clearly as you can the interior of the unit with all the wires/components showing. Then post the pictures back here and we will endeavour to work it out. Here is a link that shows how to add the pictures to your question.
Adding images to an existing question
3. Contact Koss and ask if they will provide you with either a User guide or the connection details. I have searched their website but they make no mention of this particular model, (even in their "history of the company" section where they list a lot of models). Here is a contact link.