The first OBOE installation (British invention, modified by M.I.T. RADLAB) was made in a 322nd BG Marauder on January 25th, 1944. It consisted of a 400 pound apparatus with the antenna, modulator inverter and voltage regulator in the rear bomb bay and the receiver, filter and control junction box in the Navigator's section. The apparatus was a radar beacon (also termed a transponder) which was tracked by two coastal radars a hundred miles apart (Cat and Mouse). The secrecy that surrounded the blind bombing systems of WWII was such that little historical material forund their way into normal archival files. So secret was the equipment that this initial installation was kept under continous MP guard, even the use of the term "Pathfinder" was restricted. The 1st Pathfinder Squadron (M) provisional was activated on February 16th, 1944. It consisted of highly experienced aircrews from 322nd BG, 323rd BG, 386th BG, 387th BG and 391st BG. By end of February 1944 the squadron consisted of 11 Marauders and 345 Officers and Enlisted Men. After a year the force was 30 Marauders and 31 aircrews.