These will read as AC coming out of the booster and on the rails. Technically they are not TRUE AC, but rather PWM AC.
Special information regarding the Powercab only:
Reading track voltage correctly on DCC can prove to be a challenge. The voltage available on the rails is a Digital PWM form of AC, not standard AC.
For this reason often times a regular meter will not give accurate readings on the rails or on the two-pin plug out on the back of the Powercab panel.
However, the Powercab Power Supply output is Standard DC. The power supply that was included with your Powercab may be one of several versions based on what was available to us at the time. The question is the voltage and current ratings of the actual power supply you have. Printed on the power supply you should see a voltage rating and a current rating. Something like - 12v dc or 13.8v dc. and 1.35A, 1.44A, or 1.8A current rating. If you have a 12v power supply, I would consider the 10.8v reading on the rails to be correct given all the possible variables.
To adjust the track output voltage on a Ph-Pro system box, a PB105 booster, or a PB110a booster, watch this Video on YouTube - https://www.youtube.com/watch?v=YT48PwfgX7A
The 5amp and 10amp PH Pro Systems, the P105 and the PB110 Boosters can all use either AC or DC Power Supplies. Maximum input voltages are 18VAC / 24VDC
The P515 we sell for use with the 5amp PH Pro is 15VAC
The Brutus we sell for use with the 10amp PH Pro is 18VAC.
The PH Pro System Box, the P105 and the PB110 all have a voltage adjustment potentiometer inside the box that can be accessed from a small hole in the rear.
This allows for flexibility and voltage matching to other boosters as needed.
The PH Pro and PB105 are used for Z, N, HO, and S scales.
The PB110 should be used for O and G Scales only, unless voltage is lowered by the end user and proper circuit protection is added for use with smaller scales.
Because of a change in Federal Regulations we were forced to change power supplies on any new products going forward The new power supplies are all DC Switching Power Supplies with the required power factor correction. This new supply has two output options: 12vdc and 13.8vdc with a switch on the supply. This new supply is being used in all of newer products such as the PB5, SB5, and DB5. All new Products going forward will be required to be sold with this type of supply. To sum up, the power supplies are fixed, the adjustments are in the System boxes.