The simulator operates over the GND to Battery range. Two types of batteries are supported : 12V and 24V.
Nominal operational voltage for 12V battery is between 0 volts and 4.5-16V. Nominal operational voltage for 24V battery is between 0 volts and 16-27V
When an input is grounded by the ECU, the ECU ground voltage may be up to–1.0 to 1.5 volts as compared to the simulator's ground.