Hi all, Am working on a CAT generator with negative ignition voltage instead of positive, I need to set up another device (modem) that uses positive voltage to start up on this generator, can someone assist on what to do to get positive voltage from this same source to power my modem. Some1 said it is possible using a relay timer, can anyone help out?

I need a wire that will remain positive and steady when the ignition is on and goes to zero immediately the ignition is off but what is available of the CAT generator is -ve so I need this -ve to be +ve. Thanks