Reliable Legacy Power for Essential Field Test Equipment Keep your trusted legacy fiber optic and RF test sets running strong. This 633-27 replacement battery is a Nickel-Metal Hydride (NiMH) pack delivering 22.68Wh (2100mAh) at 10.8V, engineered for a wide range of professional field testers from Anritsu, TTC, Acterna/JDSU, and others. It's the direct, compatible power source to maintain productivity with your critical T-BERD, Site Master, and OTDR equipment.