Dont know why it wnt work chris, but I got 2 of those cables and neither works. Thanks for the info, link to the dual boss pedal, but dont want those as not running power cable, dont need the led.
Just to be clear then, I have 2 boss single FS -5U switches as seen above. I connected one to the 1&2 ext switch jack on the FC12, and connected the other to the 3&4 FC12 ext switch jack. These worked fine, I use one for amp level +1 db & hold for Tuner & the other one I used for amp level -1 db & hold for Master layout, works great. THen watching the video, thinking with a splitter cable I can then buy 2 more FS-5U's and therefore use all 4 switches connecting a TRS from FC12 to double female , and each FS5 is connected to the female end of the splitter with a normal ( non TRS ) mono cable....
But as I say when I do that the switch doesnt work at all no message getting to the FC12 when you press it...and I have tried both cables and no good on either..
have just been on amazon & bought these, so will see if this will work instead...
Amazon product ASIN B00BEJWNR4
TRS out of FC into the female plug , and then connect the male ends to 2 FS5u's....fingers crossed
thanks for all the responses & help, will report back once the above turn up etc