Light Marker Distress, NSN# 6230-00-892-5192. Orange Survival light clips on to pilots harness for emergency rescue or light. New, Government Issue. Uses weird AA style batteries, that are difficult to find. New, dated 11/87. Two BA-1328/U batteries (NSN 6135-274-4035) are required for operation. These are cylindrical with a diameter of about 5/8 and maybe about 2 long. The center contact and the case contact are on the same end. This is the case with most cylindrical batteries that do not have an insulating outer sleeve. The Bren-Tronics BT-70263 is a replacement 1.5 Volt battery. Use some Aluminum foil to contact the bottom of a standard AA cell and bring the negative contact up to the top, but not touching the top contact. Insert two of the modified batteries positive end first into the SDU-30 and it will work. Rechargeable AA cells Some rechargeable AA cells, like the Duracell DHAA120 NiMH, have a case negative terminal right next to the top positive terminal. All that's needed to get them to work with the SDU-30 is to trim off a little of the outer wrapper and remove the plastic washer.