It's time to update my relay-driven controller. I'm trying to add continuity check at the handset as well as (currently only at) the pad control box.
The handset and pad controller are currently powered by a car battery at the pad, and connected by up to 500' of Cat5. I'm resorting to transistors to drive the continuity check, since it didn't make sense to use an out-and-back current flow to do that function.
Since I've never worked with transistors before, can someone with more skillz than me look this over?
...if the attachment doesn't work, the schematic can also be downloaded from here as a pdf. Or, the pages are as images here (page 1) and here (page 2).
All the best, James