Proceed PAV/PDSD Communication Cable

Does anyone know where I can find the communication cable which connects the two units. I have the six Bettercables interconnects which connect the audio channels between the two units. I donot have the phone jack type modular cable which is required for the two units to communicate. I tried with a regular phone cable. Although it fits the jacks but doesnot work.
The manual says its a modular RJ-11 cable. I got a RJ-11 cable from store(its a phone cable) which doesnot work since the PAV/PDSD has six pins as opposed to four on the phone cable.
Regards,
Girish