The Default telkom cable has a pin layout of:
9 pin 9 pin
PBX PC
3 ------- 2
5 ------- 5
8 ------- 7
This works with a PC, but the Buffer Requires the following:
9 pin 9 pin
PBX Buffer
3 ------- 2
5 ------- 5
8 ------- 4
The 7 must be on 4 for the buffer to work.