Power supply is assumed to be negative ground. If the DUT utilizes a positive ground, then the test set-ups shown in the figures need to be adapted accordingly. The power supply voltage shall be between 13 (±1) volts unless otherwise stated within this specification. For regulated power sources (e.g. 5VDC) the supply voltage shall be maintained within ± 5 % of the nominal. Power shall be supplied by batteries and/or a linear power supply. The requirements regarding ambient noise level shall always be fulfilled. When an automotive battery is used, the battery voltage shall not fall below 12 volts during testing. The battery may be charged during testing, but for test methods RE03, and CE02, only a linear power supply may be used for this purpose. If the power supply is located outside of the shielded enclosure, a bulkhead RF filter may be used to prevent stray RF signals from entering or leaving the shielded enclosure. Artificial Network design and performance characteristics shall conform to CISPR 25, ISO 11452-1, or ISO 7637-2 where applicable. The power supply return shall be connected to the ground plane, at the location between the power supply and the AN(s). In the AN(s), the unused RF port is always terminated with 50 Ω load. The number of ANs required depends on the intended DUT installation in the vehicle.