, whsmen garrison phase. , In gencral, the garrison phase from 17 November 1952 to 31 Hay 1953 was one of rehabilitation and maintenance of 5 . cquipment. Sone now cquipment was installed, but this served chiefly as an improvement to current fad lities rather than an increase in * the communications nctwork of the PPU. | ' During the build-up and carly operational phaae of CASTLE, the following major chances in facilities were planned and carried out: a. A major modification of Building 15 to provide a relay eenter with on-line ercryption on tho major circuits, a facilitios con1 trol, an extension on the crypto vault, and a new dial exchange, ‘ f b. An extcnsicn on the Joint Trensmittcr Buiiding T4, and instal” ation of additional transmitters and construction of additional antonnis, C “ . Expansion of the telephone cable plant. d. ‘Tho installation of Comeenters at Site TARE, andNaN in support of AEC operctions, and the Anstallation of Comconters at Head- 4 . quarters [TF SEVEN at ELLER and Headquarters, 16 7.2 at PRED, ee ar Ce . . , whee At the start of the ‘CASTLE Operation, the ‘detailed List of Signal facilities was quite dence, and is attached forr information, . w 30 Opersticnss . sie BS oo oon on oe Rot After it, the Communications Sect:n ado proparations for oy . the disposi tion of commund.ca ion ‘equipment deemed to be in excess to. requiredents for“garrison éperations Upon,completion ‘of this activity, “coraindeat or a | ctivities wore purely routine until the beginning of “¢ “ae the build-up phaeo AP oy NN to oy a