[AndiiT]

Hi, the red and white of the line cord are most likely the A and B wires, you could connect these to your exchange line and use the phone as a "two - wire" device.
Conversion was nescassary on many phones to ensure ringing on an incoming call and prevent bell tinkle on extensions when dialing, these days there are many two - wire phones around anyway and with the advent of DTMF dialing bell tinkle is less of a problem.

Regards

Andrew