How have you connected the RJ12 to your cable? Pin 2 is + for channel 1, pin 3 is gnd (-) for both channels and pin 5 is + for channel 2. However - its a little mysteries how GHL connect the pins and how they count them I´ll think that it is this way. The flap in direction from you. I have noted that they use different colours for the different pins sometimes - I think its differ between L and S cables. This is an old L cable with the cables mounted (from pin 1 to 6) in this order Black, Brown, Red, Orange, yellow and green. another combination I have seen is (pin 1 -6) white Brown, green, yellow, lilac and red
Hope it helps
Sincerely Lasse