This is the Ultimate Battery Backer from Electronic Model Systems. This is a device which switches between main and auxiliary battery packs depending on the voltage difference between them. FEATURES: Works with 4 or 5 Cell NiCD packs. Works with 6Volt Gel-Cell or Lead Acid batteries. Universal connector works with Hitech, Futaba, and Z connectors. Main and backup batteries must be the same number of cells and the same voltage. Capacity of the two packs is not required to be the same. Simple wiring and installation Optional remote backup indication Optional inflight backup indication 60 Amp MOSFET devices used as battery switches. MOSFET device ON resistance of 0.018 ohm or less for minimum voltage loss. Lightweight device INCLUDES: One Battery Backer with pre-installed conenctors One Instruction sheet REQUIRES: Two receiver packs SPECS: Length: 39mm (1.54") Width: 37mm (1.46") Height: 19mm (0.75") Weight (without conenctors): 0.6 oz Voltage switch: When main pack falls 1.2 volts below auxiliary pack COMMENTS: If both packs fail, the backer will switch to whatever pack has higher voltage. cmc 12/31/01 ir/kh