On October 9, 2015 at 20:47, oxguy3 said...
• I've checked that the pins should be correct for my cable (according to the store page, it's Pin 2=Tip, Pin 3=Ring, Pin 5=Shield).
This is wrong. The correct pinout for a URC serial remote is this:
[Link: remotecentral.com]
The cable you have would work on a serial Pronto remote.
