What you are referring to as the hobbs switch I assume is the switch labeled as 5-8 bar switch in the picture. This switch is used for pressure management and is only attached to the pump switch. The line out the bottom is the water hose.
The two wires from the HSV are red and brown (you may have a green wire on the other side of the plug you have). The red goes to a constant 12v+ source. The brown is the driver wire and is connected to a pulsed ground - an injector driver. Check with the others using it on your make what they are using for the drive reference. Either report back on their use or invite them to join the forum!
There are some implementations where the injector manager is also monitoring the pressure switch circuitry and making comparisons for fault monitoring purposes but the HSV and the swtich circuits are not connected.
Note: I am trying to keep this site as commercial free as possible, while keeping it useful. See policies. Not a biggie still new and starting out. Obviously on implementation the need to discuss a brand of kit remains necessary but not a dealer of the brand.