This is the Hangar 9 DVT - Digital Voltmeter and Tachometer. Experienced modelers know that the only way to be sure if you have enough charge left to safely get in that last-minute flight is with an accurate digital voltmeter. In fact, most experienced modelers won't go to the field without one. Another indispensable field accessory is a tachometer, which is used to check and compareengine performance, set needle valves, and conduct various other performance functions. Now Hangar 9 has consolidated these two field accessories into one convenient, compact unit.A great combination is Hangar 9's new Digital Voltmeter and Tachometer (DVT™) combines a digital voltmeter with a built-in load for 4 and 5 cell receiver packs and a 9.6 volt transmitter pack with a tachometer that accurately reads in 10 rpm increments for 2-, 3-, or 4-bladed props. The tachometer function reads up to 29,000 rpm in 10 rpm increments. Plus, the unit automatically turns itself off after two minutes, if not in use, saving the 9V battery ( not inculded)..The voltmeter function features a switch that allows both JR and Futaba polarity transmitters to be selected, so all brands of transmitters can be used. The DVT places a 240mA load on 4 cell packs, a 300mA load on 5 cell packs, and a 400mA load on 9.6 volt transmitter packs. Plus, a low-battery indicator shows when the 9V battery is low.Hangar 9's DVT combines two vital field accessories into one convenient package — a must-have field box item for flyers of all skill levels.