A range of on-board battery voltage monitors has been introduced. The monitors are supplied with a selection of plug-in resistors marked 4.8v, 6.0v, 7.2v, 8.4v, and 9.6v to enable the monitor to be used with NiCad batteries with 4 to 8 cells. In operation the unit is installed in a visible place on the model with double-sided adhesive tape or two screws through the rubber grommets. The display has three red, four yellow and three green LEDs.